Personally, I ask whether it's allowed or not before I give a tip just to be sure, and I do this in general especially if someone assisted me patiently or helped me with my concern.
Most of the time casino allowed tips to there dealer because this is normal on gambling industry actually it’s very rare to see a casino that doesn’t allow any tip for their dealer. On US casino. Players should tip the dealer for every certain amount of time they spend on that dealer table as a customary. You shouldn’t be hasty on tipping because it’s a gesture on appreciating someone service. Customer is always right and you will be gently notified if that’s not allowed because you are important to the casino as player. Just tip whenever you feel on doing it.