We were not presented with a bill, but they do ask your room number. I would would be wary of tipping on a credit card simply because you're not really sure if the servers receive it at the end of the stay since they don't handle credit card charges at the restaurant/bar.

As for the tipping controversy -- whoa, calm down. Didn't mean to start a thing. We are American and here it is customary to tip for service whether it's at a restaurant or in your room.