The sales tax would probably need to be exempt on some other stuff too (utilities - easy enough? clothing - extremely difficult. Are there other household items - then it gets difficult? some countries exempt non-luxury food only, etc? what other services should be untaxed? does transportation mean a car? a new car? a car of only a certain value? petrol? repairs? medical care? a bed? a king size bed? school supplies?).
Plus, if you need to raise the best part of $1 trillion then the tax will have to be a high percentage... probably at least 20%, maybe more.
See -
http://www.bea.gov/bea/dn/nipaweb/nipa_underlying/TableView.asp?SelectedTable=19&FirstYear=2003&LastYear=2004&Freq=Qtr
I reckon you could easily trim out a half of those expenditures as ones which low income people should avoid tax on. Leaves maybe $4 trillion taxable expenditures...
If you want $750b of income tax out of potentially only $4t, that's getting close to 20%.