Currency conversion can be a pain. I know my experience in Canada has always been that retailers are happy to take US $$ and give change in Canadian. Makes for a big profit on even small purchases for them.
Currencies have differing values and people need to be prepared to deal with the conversion factors. I don't see people in the EU asking that Euros be accepted as US $$. Of course, the value is reversed in that case.
I'm not trying to be a jerk, just pointing out that US and CAN $$ are not equal values. If I'm dealing with a foreign entity I expect to deal in the currency they sell in.