I think the best answer to your question is:
First of all grades obviously matter. If you have a 1.0 you will get kicked out of your program. If you want to apply for a residence you will not get in with a 2.0. They need some criteria to weed out the applicants and while I am sure they miss a few gems with 2.0's, they generally don't.
That being said, grades have no correlation to your performance as a pharmacist. It does not matter what you got in pharmacy school if you don't know your stuff when you are out there in the real world.
If you want to get a 4.0 because you get a scholarship or because it gives your personal satisfaction, then go for it. Just don't think it will make you a better pharmacist.