I'm going to get a mani/pedi today for the first time, how much do I tip?

The only other time I ever had one was a wedding gift from the person who gave it to me, so I have no idea how to figure out the tip. Is it 15% like a restaurant? Also, the person giving it this time might be the owner, do I still tip then? I'm using a groupon for it,, but I know to tip on the full amount, I just don't know how to determine what that is. Thanks!