We tip 10% to 15%. Remembering to discount the 13% GST first. Actually, many tip the GST amount since it's already calculated for them. You can tip in U$ if you want. I know my own bank will convert a small amount for free and I have a U$ account for that time we might take a trip south. Many people do. Not so well paid service industry people will likely appreciate a C$ tip they can use without conversion though.