Without a doubt YES! I love to do mid-night until dawn chip "hunts" when in Vegas. At this point, several early morning employees now know me by sight, they smile and start digging for chips before I'm even at the window. Trust me, it's not because I'm cute, polite (always!) or try to tell them a clean, cute joke.....they KNOW I tip!! In return, I have gotten my paws on some awesome chips and obsolete silver strikes.
The trick is to walk up to the cage with money in your left hand. As you explain what you're looking for, silently slide more money up towards the right side of the counter - they know it's tip money. I have even had several go to the back (they usually have plenty of time during early morning hours as no one else is in line behind me) and return with some really cool stuff. I never take any of the tip money back if they find me chips, but I have happily surprised a few by adding more money to the tip pile as I scoop up my "treasures". I have even had a cashier suddenly hand me a coupon for a free breakfast buffet after tipping her.
If anything though, for a few measly bucks, I have made friends with some of the cashiers over time, and it makes me feel good to see them smile.
Aaron, if you want to go on a "midnight chip hunt" with me while at the convention, just drop me an e-mail!.....it'll be cooler at night and I always wind up my trek with a good breakfast afterwards!