@gogobonobo That’s not how tax deductions work.
Let’s say they make a profit of $10 of a sale and you give them $1 for charitable deductions in addition.
The store now has $11 profit (but gives $1 to charity). The tax deduction lowers their profit from $11 to $10.
It’s exactly the same as if they’d not gotten the extra $1. It just goes to charity.