If you support just one currency in your payment process, you can still accept payment from foreign currency cardholders. However, the currency exchange rate will not be applied until the funds are removed from the cardholder’s account. This means that your customer cannot know the exact cost of their purchase at the point of sale.
If you expect to make a lot of sales in currencies other than your own, you can solve this problem by using Dynamic Currency Conversion or Multicurrency management
At the point of sale, the customer is shown the current exchange rate and the converted transaction amount. They can then decide if they want to pay in their own currency at this exchange rate.
Multicurrency allows you to price in the currencies that you want to support.