Do you need to use Canadian dollars or can you use US dollars?  You need to exchange your US dollars at the Cashier Cage within the casino as the machines will only accept Canadian money. I have always found the exchange rate to be acceptable so it is not necessary to purchase Canadian currency before you arrive.

According to Paragraph 40(2)(F) of the Income Tax Act, gambling winnings, whether from online or land casinos, sports betting, or horse racing, are tax-free for Canadians, no matter the province.