The sales tax varies province to province. There is a federal GST set at 5%, then each province may choose to have a PST, or combine the two to charge a HST.
From what I've seen, it is reasonable to assume that the iPhone 4 price will be as follows in Canada:
32GB/$749
16GB/$649
That is for the direct from Apple prices. But from your post I think you know that already. I can't see the prices being any higher, who knows. Rogers/Apple Canada need to get this info out there quick!