Unless there’s some oddity with a Canadian 50c piece (not being minted anymore, limited runs, etc) you should be able to get any denomination of legal tender from a bank for face value. I know my father regularly exchanges bills for a roll of $1 (USD) coins just for the novelty and their convenience with vending machines.
I suppose there might be some limitations that the bank imposes (minimum amount to exchange, must be a member of the bank, etc).
Wouldn’t it be easier to just go over to the bank and ask, rather than putting the question to random people on the Internet?
Apparently they only carry 50 cent pieces when someone gives them to the bank. The teller told me that she has some a couple weeks ago, but no one at the bank had any.
I could buy some from a post office, but they are in a display case that is a rip off. I’m not gonna pay 10$ for a 50 cent piece in a display case.