1. Let the federal government establish a uniform national sales tax and outlaw all state and local sales taxes.
2. Even better, eliminate sales taxes entirely. Replace it with higher income taxes or property taxes. Yes, yes, I know, regressive, not progressive, taxing consumption is better, but there's something to be said about an economy without crazy levels of bureaucracy and regulations.
3. Just keep fighting off the states until they accept that Internet orders should be non-taxable. The Internet has completely changed the business models of music delivery, porn, and newspapers. No reason it can't eventually convince states to back off on sales taxes.