Usually when I see a coin on the ground, I will pick it up. Is it ok to take those coins or should I just leave them?
See no reason why one should not pick up any coin on the ground. One may think it is against the precept of not taking what does not belong to oneself, but it is the intention that matters. If one feels bad about it, it can always be drop into any donation box where the money can be used for some good cause.