The Donations app can present and process payments in Canadian dollars, British pounds, or Euros for sites using Authorize.net, Braintree, CyberSource, PayPal Website Payments Pro, Stripe, and TouchNet. Non-US currencies are not currently supported for customers using iATS.
Only one currency type can be used per Soapbox site and your payment processor must be setup to allow for the currency you wish to use. Integrations with Salesforce also require that the underlying Salesforce instance be setup to handle the chosen currency.
To alter the currency used by your site, please submit a ticket.