If I remember my economics courses correctly, a tax on retail purchases will tend to depress retail sales, further depressing the economy and killing jobs.
Competent accountants and lawyers can help their clients reduce their income tax burden. It isn't easy to do this with taxes that are embedded in the process of buying and selling (sales tax, motor fuel taxes, etc.).
The final costs can be significant. I talked to a manager of one store who claimed that a specific bra in her store costs $32, but in Canada, the same bra would cost $100. Now, I guess it was a special size, like an 'F' (I didn't even know that size 'F' existed), but still, you get the point.
I never took economics courses, but further taxing retail purchases will certainly lower sales and keep the economy down. It will also make American products less competitive, with every phase of production inflated in price from what it used to be. Will this same VAT system be imposed on products made in China?