Selecting your base currency is one of the first steps when setting up SC Commerce.
To change your shop currency settings go to: SC Commerce > Settings > General > Currency Options and select your desired currency from the currency drop down.
If your currency is not listed in the dropdown, you can use our code snippet to add your own custom currency.
SC Commerce only allows for one base currency at a time. There are a few extensions that allow you to offer multiple currencies. You will need to research these and select the best solution for your shop.