Credit Card fees will vary depending on the merchant & gateway provider you use. The fee is imposed by the vendors and is not dictated by RaiseDonors.
Here are the current gateways supported by RaiseDonors with links to each so that you can explore their cost structures.
Stripe - https://stripe.com/us/pricing
Authorize.net - http://reseller.authorize.net/application/?resellerId=25260
PayPal Website Payments Pro - https://www.paypal.com/us/webapps/mpp/paypal-payments-pro
For a list of supported currencies, click here.