I'll tip a dealer, on a cruise ship, if they make an effort to make the game enjoyable. I like an interactive and fun table. If I win I usually tip about 10% of my winnings. I have tipped even when I've lost if the dealer(s) let me have fun while I gave them the money.
I wouldn't even think about tipping on a slot win. The machine can't pay out the winnings, or the jackpot needs to be verified, so an attendant is basically giving you the money the machine should have paid.