It depends!

I have had drivers who really made me feel uncomfortable by telling me over and over again on the journey how poor they are and how expensive it is to live in JA. Almost trying to guilt me into giving them a big tip. I usually give them very little.

I have had drivers who are very personable and a delight to have met, I usually give them between 20% and 25% of what they are charging.

If a driver just picks me up at point A and takes me to point B without much conversation and his cab is clean and comfortable, I will tip approx. 15% of the fare.