Tipping is one of those issues that every vacationer gets running on his or her head. Customs and traditions regarding tipping vary from region to region, and are generally dependent on the personal opinion of the traveler. For some people, specific amounts or percentage of the bill should be given, while others think that people should not be obligated to tip at all.
In the United States, it is somehow mandatory to tip between 15% to 20% of the total bill, depending on extra services. I once read a story of man who ate in a US restaurant and did not give a tip at all. The manager then probably went after him and scolded him for not giving a tip.
Meanwhile, in others places, especially in the more impoverished regions of the world, people hardly give any tip, if at all. Some give around $1 as tip, regardless of how much the bill is. But the thing to remember about these countries is that there's already an added 10% service charge on top of the food that customers pay.
In Costa Rican restaurants, it is general that the local people do not give tips, although an added 10% tipping fee on top of the taxes are usually added to the bill. If you're North American, I am certain that this is still low, so you could always add some amount to this as you please.
Cab drivers are a different story, because they are really usually not tipped unless there has been some extra services given, like helping you take out your luggage at the cab's trunk, for instance. Tipping chambermaids, bellboys, and nature guides are also customary, but the amount really depends on the quality of service given.
As for the currency, you shouldn't worry about giving US dollars because they are generally accepted as tips.
But then again, if you feel like you should not tip, then you can always do so. This is not North America after all. It is Costa Rica, where you can always enjoy as you please without the added charges.
