Why?
I'm from New York, where we have both a sales tax and an income tax. Like the income tax, the sales tax is gerry-rigged to appeal to different constituencies. High taxes on cigarettes, no tax at all on food, and infrequent "tax amnesty" periods on things like clothing to boost sales (which are then taxed as income) and allow the politicians to pretend to be against high taxes.
Spreading this repressive (and hugely expensive) system to the entire nation is insane.
I prefer a flat tax. It fits within the (admittedly horrid) system we already have, it's fair, and it has no hidden gotchas.
And before anyone says, "Oh, we'll have just the national sales tax and get rid of the income tax" forget it. I haven't even seen a proposal to amend the Constitution to eliminate the income tax. It's NOT going away.