In nopCommerce, only primary store currency is used, which is the currency
against which all other allowed currencies will be configured. Although
nopCommerce allows having multiple currencies for displaying your product
prices, the primary currency is used for payment transactions with online
payment gateways.
If you are using an online payment gateway (such as, PayPal, Google
Checkout) the amount is sent to the payment gateway and will be the price you entered in primary store currency.
Primary store currency is used by the store administrators only. It is used for
setting product prices and does not have to be the same as the published
currencies.
If you have only one published currency, the store will not display a currency
selector, or any currency symbol with prices. If more than one currency is
published, all prices are marked with the currently selected currency.
nopCommerce recommends removing any currency that is not required.
nopCommerce uses an exchange rate to calculate the amounts for published
currencies. The exchange rate is entered when a currency is added or edited. Or you can use a real-time exchange rate service to calculate the amount, and the price of the product is multiplied by the exchange rate provided.
Exchange rates fluctuate on a daily basis. Therefore, you can edit the exchange
rate as often as you need in order to stay current. Actual transactions are only
handled in your store's primary currency. On credit card transactions, banks
will usually make exchanges automatically based on the most current currency
values.