Going off what Randy said, it depends on where you are performing. School or random street performances = forget about it. However, a paid gig at a restaurant is something different. I don't get tipped a whole lot for magic, but I also make balloon animals for the kids, and I make BANK in tips from those. I sometimes also perform Sponge bunnies for the kids, and the adults love it too, so I get tipped from that too. If I perform for a couple in their mid 20's, however, I'm not really expecting a tip, but I do have a lot of fun performing for them.
Also, higher end places will probably generate more tips because, as Rick said, those people "have" the money to tip you and pay for a meal. At a more kid generated place, most parents aren't willing to shell out 5 or 10 extra bucks plus a meal when they have several kids. I know that kind of contradicts what I said earlier about me getting good tips with balloons, but that's because balloons are something physical, and the parents usually feel like they have to pay. If they ask me how much they are, I say "they're free if you want them to be" and I usually get a tip anyway. Granted it might be only 2 or 4 bucks, but those can add up. And the occasional larger tip always helps too.
Sorry I rambled a bit haha. Anyway, I hope that helps you out!