1、获取当前店铺的货币方法：
  当前店铺的基准货币：$baseCurrencyCode = Mage::app()->getStore()->getBaseCurrencyCode();
 $CurrentCurrencyCode = Mage::app()->getStore()->getCurrentCurrencyCode();
 $CurrentCurrencySymnol = Mage::app()->getLocale()->currency(Mage::app()->getStore()->getCurrentCurrencyCode())->getSymbol();
 $CurrentCurrencyName = Mage::app()->getLocale()->currency(Mage::app()->getStore()->getCurrentCurrencyCode())->getName();
2、获取自定义货币的符号，code,返回的是一个二维数组
  $currencyDate = Mage::getModel('currencysymbol/system_currencysymbol')->getCurrencySymbolsData()；
//获取系统默认的结算币种
$baseCurrencyCode = Mage::app()->getBaseCurrencyCode();

//获取所有系统可用结算币种
$allowedCurrencies = Mage::getModel('directory/currency')
    ->getConfigAllowCurrencies();

//获取两个币种之间的汇率
$currencyRates = Mage::getModel('directory/currency')
    ->getCurrencyRates($baseCurrencyCode, array_values($allowedCurrencies));

下面是几个常用的货币转换方法。需要注意的是，凡是涉及到两个币种之间转换的，都必须确保系统中已经导入了两币种之间的汇率。更多币种之间的方法可以到directory/data助手类中找到。

// 将100人民币转换为美金
$Price = Mage::helper('directory')->currencyConvert(100, 'CNY', 'USD');
//将100美金转换为人民币
$Price = Mage::helper('directory')->currencyConvert(100, 'USD', 'CNY');

汇率的导入：
magento后台currency rate页面有个Import按钮：

点击import导入货币汇率。
汇率导入的方法：

class Mage_Adminhtml_System_CurrencyController extends Mage_Adminhtml_Controller_Action
{
    public function fetchRatesAction()
    {
        try {
            $service = $this->getRequest()->getParam('rate_services');/*后台Import Service 的值*/
            $this->_getSession()->setCurrencyRateService($service);
            if( !$service ) {
                throw new Exception(Mage::helper('adminhtml')->__('Invalid Import Service Specified'));
            }
            try {/*实例化Webservicex这个Model，magento自带的是Webservicex*/
                $importModel = Mage::getModel(
                    Mage::getConfig()->getNode('global/currency/import/services/' . $service . '/model')->asArray()
                );
            } catch (Exception $e) {
                Mage::throwException(Mage::helper('adminhtml')->__('Unable to initialize import model'));
            }
            $rates = $importModel->fetchRates();
            $errors = $importModel->getMessages();
            if( sizeof($errors) > 0 ) {
                foreach ($errors as $error) {
                    Mage::getSingleton('adminhtml/session')->addWarning($error);
                }
                Mage::getSingleton('adminhtml/session')->addWarning(Mage::helper('adminhtml')->__('All possible rates were fetched, please click on "Save" to apply'));
            } else {
                Mage::getSingleton('adminhtml/session')->addSuccess(Mage::helper('adminhtml')->__('All rates were fetched, please click on "Save" to apply'));
            }

            Mage::getSingleton('adminhtml/session')->setRates($rates);
        }
        catch (Exception $e){
            Mage::getSingleton('adminhtml/session')->addError($e->getMessage());
        }
        $this->_redirect('*/*/');
    }
}

下面是Webservicx的文件路径：

说明:
$rates = $importModel->fetchRates();这不调用的方法在下面可以找到：

abstract class Mage_Directory_Model_Currency_Import_Abstract
{
/*Webservicex继承这个Model*/
 public function fetchRates()
    {
        $data = array();
        $currencies = $this->_getCurrencyCodes();/*获取website所有允许的货币code*/
        $defaultCurrencies = $this->_getDefaultCurrencyCodes();/*获取website中默认货币code*/
        @set_time_limit(0);/*设置程序执行时间，为零表示，执行直到程序结束（因为要去第三方获取资源，所以较长）*/
        foreach ($defaultCurrencies as $currencyFrom) {
            if (!isset($data[$currencyFrom])) {
                $data[$currencyFrom] = array();
            }

            foreach ($currencies as $currencyTo) {
                if ($currencyFrom == $currencyTo) {
                    $data[$currencyFrom][$currencyTo] = $this->_numberFormat(1);
                }
                else {
                    $data[$currencyFrom][$currencyTo] = $this->_numberFormat($this->_convert($currencyFrom, $currencyTo));
                }
            }
            ksort($data[$currencyFrom]);
        }

        return $data;
    }
}

根据以上几个方法，可以写一个定时任务，按时更新store的货币汇率