This is definitely not the case. If you make $100 profit and you would have had to pay 20% corporate tax, then you pay $20 in taxes, you'd be left with $80 to buy chocolate or whatever you want.

If you donate $20 and deduct it from your profit, then your profit is now calculated at $80. So you pay $16 in taxes. So you saved $4 but spent $20, so you're $16 dollars down and now you only have $64 for chocolate, so not 'essentially nothing'.

Unless you're positing some very specific, unusual situation, this isn't how tax deductibility works. The dollar amount of a tax deductible donation is subtracted from your taxable income, not from your tax bill. So you're getting a discount on the donation equal to your marginal tax rate.

That's not how tax deduction works.

Example:

You earn $100,000.

You donate $10,000 to a qualifying charity.

You can now deduct that $10,000, i.e. you’ll be taxed as if you earned $90,000, not $100,000.

If your marginal tax rate is 30%, you’ll save 30% of $10,000 = $3,000 in taxes. So you’re still out $7,000 in real money.