Exchange rates are set centrally, and the local banks then add something for their profit etc, unless you are sending very large sums then in my experience there is very little difference, assuming sending 1000US$ or thereabouts. Small sums can be a little different, a lot of banks are not interested in these and set the profits accordingly.
Traveller is on the money; you won’t find a big difference from bank to bank because they all follow the government issued rate.
Cheers,
CK
Within Taiwan, they seem pretty reasonable on spreads. Don’t exchange in the U.S. or Canada, though, as they will eat you alive. The Canadians in particular are greedy shits, whether you’re at a bank, the airport, or a restaurant.
Oh-oh! Ma-Po’s onto us! Guess we’ll have to stop milking all the tourists who cross the border into glee and throw their money around like paper because it’s worth so much more than the Canadian dollar! 
Actually, the reason shops and restaurants usually undercut the exchange rate in Canada is because a lot of tourists come up with their greenbacks and can’t seem to be bothered to stop at a bank and get some CDN$. Think about it, if you’re in a foreign country, you should use their currency, otherwise you’ll get fleeced. The only country I know of where this may not be the case is Indonesia, where being a money changer seems to be a national passtime. 
Cheers MaPo, and watch out for that Starbucks at the Vancouver airport willing to take those US$ at par! 
CK
Why do we even have different currencies for the two mostly white, English-speaking countries in North America anyway? Seems kind of pointless with all the millions of people crossing the border everyday. It’s like having to change money every time you cross the bridge from New York to New Jersey, or something. Hell, we’ve already got NAFTA - time to phase out the separate currency annoyance.
It’s not just the shops and restaurants. The USD-CDN exchange spreads at banks and currency exchanges are ridiculous – you’re better off using a credit card and taking the (MUCH smaller) hit from the card agency, in my limited experience. IIRC, the spread was over 10% back in 1999, and this was in the banks in Vancouver, not some hotel bar or whorehouse.
For USD-NTD and CDN-NTD, in 2002 the spreads at the Vancouver airport currency exchange booths were just as bad. I converted at the booth at CKS for something like 1% and was glad I’d waited.
I thank you for your kind concern, but I would never have to worry about this – I avoid Demon Bean like the plague. 
What’s your point? Why should you stress white/English speaking countries for having the same currency? And English is not the official language of the US as there is no official language.
Further, there are some Canadians who don’t speak English, but French, and some Americans who can barely speak English at all.
But in Europe, a multitude of languages and races use the same currency making it dead easy to travel between them without worrying about exchange rates, so I do agree.
I would propose a single currency for ALL of North America, but with Canada being commonwealth, it doesn’t seem very likely. Also, who would they put on the NA dollar? Washington? NO. Lincoln? NO. A bunch of native americans I suspect.
And as it is, Mexico and Canada will gladly accept US dollars in many places.
Just not many places in the US are reciprocal.
They could all adapt the Euro. 
Explain?
What does commonwealth have to do with Canada’s choice of currency?