It's tax-related, but also because every state, city, and county can add their own sales taxes, so the only way to advertise prices for a national chain is by e

It's tax-related, but also because every state, city, and county can add their own sales taxes, so the only way to advertise prices for a national chain is by excluding sales taxes. As a result most businesses, even just local ones, follow suit. And the taxes can change after any government budget meeting or vote. Plus, many retailers attempt to keep pace with or beat inflation, so prices tend to slowly rise, by pennies at a time.