propina = tip, gratuity
A fee? Or maybe a tip? Depends on the context.
Tip
If by tip you mean an amount of money we say: propina. If by tip you mean a piece of advice we say: pauta.
The term "tipping" can have a number of meanings. One meaning is to cause something to fall over. Another meaning is to give a service worker additional money above the amount billed to thank them for their service.
A tip or gratuity is an amount of money that is given to a worker such as a waiter or waitress who performs a service for you.
a tip A bonus
To politely ask for a tip, you can say something like, "If you enjoyed the service, tips are always appreciated."
* Every restaurant is different. Sometimes when you leave a tip the money from all waitress' or waiters are pooled and divided (bus boys may get some of the tip money as well.) With other waitress' and waiters they may be able to keep the tip for themselves. Generally you tip a waiter 15 percent if the service is good. If you don't feel within reason you have had good service you do not have to leave a tip.
A discount is money off a product, a sales tax is money added to the price of a product, and a tip is money given to someone fr good service.
To ask for a tip politely and effectively, you can say something like, "If you enjoyed the service, a tip would be greatly appreciated." Remember to thank the person for their consideration.
A service tip is simply called a 'tip' or 'gratuity' and one pays a waitress; waiter; bell boy in a hotel, etc., if their service is good. A service tip is generally 15% of the total bill, but can be less. If the service is poor then one can decide not to leave a tip.
A delivery fee is a charge for the service of delivering food to your location, while a tip is a voluntary amount of money given to the delivery person as a gesture of appreciation for their service. The delivery fee goes to the restaurant or delivery service, while the tip directly benefits the delivery person.