A flat, national sales tax. Nothing else federal.
I sympathize and there is merit in this especially as more and more sales move online and are paid electronically (be it credit card or other form). Taxes could be collected by the credit card merchants at the time of purchase and remitted by them, thereby alleviating the accounting and reporting expense of retailers. Retailers would only need to file a supplemental return for cash transactions.
Retirees would complain they are footing a second round of ‘income tax’ on their retirement savings.