Ahhhhh tipping.......my favorite topic.
I tip according to the service I receive multiplied by a factor of how much I think it will affect the person's life.
Look around while you are in Jamaica. Does it appear that these people have been so "over-tipped" that have become spoiled and lazy?
I tip well for selfish reasons. I love the thought of a service provider going home with more money than they thought was possible.
It makes me feel like I am (in a tiny way) helping.
Same thing here at home.
If you see a waitress who is working her tail off and doing a great job (not just with your table but also with all of the others) see for yourself how good it feels to leave a $10 tip on a $12 breakfast.
Know that somebody else who received just as good of service as you did only left a dollar.

Just my 2 cents but put a few hundred extra dollars in your budget for a week in Jamaica and you'll have at least that much more value in your trip.