Well, when I've purchased things recently from Apple, they've added tax on top of the price. I don't know whether they do that in Canada or not. In the U.S. the rules have always been that you have to charge tax in a particular state if you have a physical presence there. I have no idea what the rules are in Canada.
Amazon is different in that they're only doing payment processing, and they don't add tax onto the transactions. Eventide doesn't know or care about what name is on the credit card used to pay for something. The only thing we keep track of is what Eventide user name the purchase should be deposited to.