Как известно Magento — это система электронной магазинов для разных стран, и хорошо реализована поддержка валют и курсов валют.
Подборка кусочков кода Magento для игр с курсами валют 
$targetCurrency = Mage::getModel('directory/currency')->load('EUR');
$price = round(Mage::helper('directory')->currencyConvert($priceToConvert, 'GBP', $targetCurrency), 2);
$baseCode = Mage::app()->getBaseCurrencyCode();
$allowedCurrencies = Mage::getModel('directory/currency')->getConfigAllowCurrencies();
$rates = Mage::getModel('directory/currency')->getCurrencyRates($baseCode, array_values($allowedCurrencies));
var_dump($rates);
echo Mage::app()->getLocale()->currency(Mage::app()->getStore()->getCurrentCurrencyCode())->getSymbol();
$price = $_Pdetails->getPrice();
$magento_style_price = Mage::helper('core')->currency($price);
$currentCurrencyPrice = Mage::helper('core')->currencyByStore($baseCurrencyPrice, null, false, false);
$fromCur = 'USD'; // currency code to convert from
$toCur = 'EUR'; // currency code to convert to
$toCurrencyPrice = Mage::helper('directory')->currencyConvert($fromCurrencyPrice, $fromCur, $toCur);
$baseCurrencyCode = Mage::app()->getStore()->getBaseCurrencyCode();
$currentCurrencyCode = Mage::app()->getStore()->getCurrentCurrencyCode();
$price = 100;
$priceOne = Mage::helper('directory')->currencyConvert($price, $currentCurrencyCode, $baseCurrencyCode);
// convert price from base currency to current currency
$priceTwo = Mage::helper('directory')->currencyConvert($price, $baseCurrencyCode, $currentCurrencyCode);
$price = "100";
$block = Mage::getBlockSingleton('checkout/cart_shipping');
$block->getQuote()->getStore()->convertPrice(Mage::helper('tax')->getShippingPrice($price));
echo Mage::helper('core')->currency($_price);
echo Mage::helper('core')->currency($_price, array('precision' => -1) );
/**
* Get the base currency
*/
$baseCurrencyCode = Mage::app()->getBaseCurrencyCode();
/**
* Get all allowed currencies
* returns array of allowed currency codes
*/
$allowedCurrencies = Mage::getModel('directory/currency')
->getConfigAllowCurrencies();
/**
* Get the currency rates
* returns array with key as currency code and value as currency rate
*/
$currencyRates = Mage::getModel('directory/currency')
->getCurrencyRates($baseCurrencyCode, array_values($allowedCurrencies));
$allowedCurrencies = Mage::getModel('directory/currency')
->getConfigAllowCurrencies();
/**
* Get currency rates for Nepalese Currency
*/
$currencyRates = Mage::getModel('directory/currency')
->getCurrencyRates('NPR', array_values($allowedCurrencies));
$baseCurrencyCode = Mage::app()->getStore()->getBaseCurrencyCode();
$currentCurrencyCode = Mage::app()->getStore()->getCurrentCurrencyCode();
$price = 100;
// convert price from current currency to base currency
$priceOne = Mage::helper('directory')->currencyConvert($price, $currentCurrencyCode, $baseCurrencyCode);
// convert price from base currency to current currency
$priceTwo = Mage::helper('directory')->currencyConvert($price, $baseCurrencyCode, $currentCurrencyCode);
$baseCode =Mage::app()->getBaseCurrencyCode(); $allowedCurrencies =Mage::getModel('directory/currency')->getConfigAllowCurrencies(); $rates =Mage::getModel('directory/currency')->getCurrencyRates($baseCode, array_values($allowedCurrencies)); var_dump($rates);