The trade is between you and the person you are trading with. There has to be at least one other person involved for there to be a trade. The government would NOT know how much money you spend, only what has been spent. Used goods would not be taxed, only new consumer goods.
Basically only retail would carry taxes. This only helps small business because it removes a very large expense of time and money from their practices. Don't even pretend that businesses pay taxes, because they don't. The end consumer does. Businesses simply pass the taxes on to the consumer in the cost of their products.
What about services? Would my handyman service be taxed?