If there is something that we cannot escape in Cuba, it is tip. It is common, it is expected so you should take it into account in all your expenses on the island. But we can help you a bit with the percentages.
For example, if it is to tip who parks the car for you you can leave them from 25 cents to 1 CUC without problem. In Cuba there are no parking meters and very few places where you have to pay, but whenever you want someone to park the car for you, you will have to give something in return. There are parking lots licensees who even have a list with official prices. 25 cents at least, 1 CUC in the most expensive discos or restaurants.
With respect to tip for hotel and resort staff As a general rule, something is left to someone who has done you a special service. If the bartender served you after hours, if the maid washed something for you, that kind of thing can be repaid with some money. A dollar or 20 CUC is fine if you stay a week. That you can spend in total.
If there is someone in the bathrooms then the bathroom is clean thanks to that person and it is convenient to give them some money as well. Between 10 and 25 cents is enough. In restaurants the tip can be between 5 and 10 percent. 10% is usually charged to the account but if they did not add it to you then that is the corresponding percentage that you should leave. If there are musicians, in the bar, in the restaurant or in the cafe, and they play music that you want, then you can leave them a dollar.
Finally, tour guides can be rewarded with 2 CUC per person per day.