On the Settings -> System screen, one of the settings is named "Store Currency Code". Here you must select the three-letter international currency code that the store is offering its products in.

SoftSlate Commerce supports international currency codes in the sense that you can select any ISO 4217 currency code for this setting. The store will look at each user's browser setting to determine the user's locale or origin. It will use the individual's locale to determine how to format the prices displayed throughout the store. For example, if your store's currency code is USD, for US dollars, a price would be displayed as $12.50 for a user whose browser settings indicated he or she is from the US, whereas it would be displayed as 12.50 USD if their browser indicates he or she is from another country.

There is currently no support in SoftSlate Commerce for selling the same products in multiple currencies and translating their prices through an exchange rate system.