One issue with the 9% is the election. If Obama can show that 999 will cost middle and lower class families more, then he will have an advantage.
The way to blunt that advantage is to exempt food NOW from the 9% sales tax. While the prebate takes care of all that if we ever get a system with only an nrst, for now care should be taken with voters in the election.
Maybe Zero will point out that 999 is 666 upside down.