[El Cid]

I give this 0.0% chance of happening. Congress derives a good deal of their power from the tax-code: the money they bring in; the special breaks they can cut; the class-warfare posturing. If all of a sudden people would see the tax they'd pay on every purchase - people would become extremely interested in understanding where their tax dollars were going.
I frankly think that a NST (exemptions on food, and perhaps housing - so the poor aren't nailed) would be great for freedom, and limiting the size of government -- but its that latter point that makes it really hard for me to see how the Congress folks would allow this to happen.
I'd like it to be so -- but it presumes the existance of a Congress that was more interested in the nation than its own power.

[concerned about politics]

I give this 0.0% chance of happening. Congress derives a good deal of their power from the tax-code:

Yes. They control the people through taxation. If they want a certain behavior,lower taxes.
If they want a certain behavior to stop, increase taxes. Look at cigarett taxes, for example.