A one percent sales tax wouldn't fund it. In 2012 we spend roughly $1.45 trillion on Social Security and Medicare. For a 1 percent sales tax to cover that you would have to have $143 trillion in taxable sales. That's considerably higher than our total GDP by a factor of 8 or 9.
If your math is correct how would using the sales tax just to fund SS work out. I am not so sure Medicare will survive Obamacare anyway.