Answer:
5-10% is good.
If the dealers keep their own tips, I would tip closer to 10%. When they keep their own tips they really appreciate it more, than dealers who split.
It's best to tip as you go. In the end, your not going to have any money left to tip, if you wait until the end. If you play only one hand and leave, then 5-10% is good.
You should tip a dealer a few bucks every now and then but if you winning it should vary from 3-12 percent. 3 percent is not like 15 percent at a restaurant so dont think of this as you do with a waitress's 15-20 percent. 3 percent if they suck, 5-12 percent depending on if you going to stay and gamble some more and keep tipping or if they were good dealers. I personally don't stick by a percent it depends on how easy the win was and etc. Just always tip if you bet a few times and win or if you stay at the table for a while even if your not winning. Amount depends, dont feel like you have to put a certain amount.