You should look into Zimbabwean dollars, Russian ruble, Venezuelan bolivar history. No amount of government intervention will help to keep the value once the population loses faith in the currency. Even if you start giving away gold bars for each unit of currency, you will quickly end up with no gold bars and lots of worthless paper. If you restrict the supply of currency, people quickly invent their own money, which you don't control.

EDIT:

And people will happily pay for goods and tolls with worthless paper, but your demand to accept dollars and fix the prices has one outcome: empty shelves and lots of people in prison (because how else do you enforce dumb demands?). Both were tried in Venezuela and USSR with the same result.