We do take cash in different dollar values to use for on board tips. If they help carry your carry on to your room, room service as an example do appreciate the extra gratitude you show to them.
We also keep on hand money, if you go on any tours, some passengers due show a gesture toward the tour guide and the driver of the vehicle.
Then we do at the end of the sailing if the waitress, asst.'s, wine steward and also room steward, if they showed exceptional service. And the longshoreman taking your luggage out of the terminal to the street side.