What kind of businesses give cash discounts?

Businesses that like to hide part of their revenue from the Tax Man (IRS). If you pay by debit/credit card or cheque every thing is tracable. Taking payments in cash also helps keep banking costs down. Hence it is mostly small businesses that give cash discounts to encourage you to pay them in cash enabling them to control costs and avoid small amounts of tax. Additionally, gas stations are notorious for offering cash discounts.