That's not how tax deductions work. Donating money to a charity at a register is legally still your donation, and you can deduct it from your taxable income. Businesses can only deduct donations made from their sales revenue. Giving a dollar to Make A Wish or whatever when you pay somewhere is not revenue a business can claim.

All charities have overhead. Go check Charity Watch or Charity Navigator if you're concerned about one.

I don't understand why this is supposed to be some "gun laws don't work" own instead of an argument for more gun laws.