[billpg]

I imagine the federal sales tax would be set to the same level as the state sales tax. States couldn't change one without changing the other.

(I've not really thought this through. The above is just a random thought. Be nice.)

[yummyfajitas]

Then states will likely raise the in-state and out of state tax to high levels, and provide rebates/subsidies to in-state businesses only.

Best not to go down that road.