You've got several payment processing options, but first of all, you'll want to make sure that your shopping cart is set to deal in the Canadian Dollar. If you don't have the option of choosing your currency please contact Support.
Here are your options for charging in Canadian funds:
PSIGate Payment Gateway - For real-time Canadian dollar credit card processing.
Manual Processing - If you have a merchant account and either a virtual terminal or physical terminal (like the ones you see in stores) to process credit cards. The cart collects all the order information and then on your terminal you can process the payment.
PayPal Standard - which is integrated with our shopping cart.
Internet Gateway & Merchant Account - This option also allows you to process credit card charges in real time, but you would have to insert their buttons code on your site.There will likely be some combination of set up, per transactions and/or monthly fee with this option. This will give you the option that is most easiest for your customers. It is also usually the most expensive as you are paying for a merchant account plus an internet gateway.