Here is a way to help out and be fair with the markets you serve. When you budget for each year, include an amount of money that you feel comfortable putting back into the community. No matter if its $100 or $10,000, the amount is not the point. Next, select one, two or three Charities that you support from a personal standpoint and let them know that you are making a contribution to their efforts over the next year.
You can't fund the almost endless requests all the time. But you can do something good for the people you believe are working on things that matter.
Your answer to those who ask is a respectful, sorry, I have already set aside funds for charitable contributions and as much as I respect what you do, I have no funds to support those efforts.
They will respect you and you can feel like you have done something good in your community.