Technically this is not a new tax. Technically Phoenix is simply rescinding the exemption for food from the existing Phoenix sales tax. Obviously the result is the same, but details DO matter.
Now, Phoenix Metro is a "metro area". About the only way you can tell which city you are actually in is to look at the color of the street signs. (and in Tempe the numbered streets go the wrong way).
Arizona itself has a base sales tax rate of 5.6%. Cities and counties can add their own sales taxes, and most do to the extent of 2-3%. The state and Maricopa Co. sales tax rates specifically exempt food purchased at retail outlets for home consumption (i.e. groceries). Other cities and counties may or may not. There is no constitutional or statutory requirement to do so.
Pinal Co, for example does not, so food in Pinal Co. has about a 0.5% sales tax on it. This is why my wife refuses to shop at the Fry's a mile or so away in Pinal Co.
The current sales tax in Phoenix itself is 5.6% state, + 0.7% Maricopa Co, + 2.0% Phoenix = 8.3%. Currently groceries are exempted from the sales tax. Thus a $1 coffee cup costs 1.08 and a $1 cantaloupe costs $1.00.
Phoenix is desperately trying to raise revenue. And pathetically so, as shopping in Tempe, Glendale, Scottsdale, or Paradise Valley is a real option for most folks who live in Phoenix.
Additionally, AZ has the system of Referendum and Recall that most states admitted after California have. This was a big part of the so-called "populist" movement at the time. Thus there is a real possibility that the people will simply pass a constitutional amendment forbidding the taxing of food in the state. Thus putting a stake in the heart of this thing pretty much for good. I can grantee someone has already written up the initiative to do so. (It's a 3 sentence initiative)
The real problem is that we have had two governors (one Dem one Rep) who never saw a dollar they didn't want to spend. Thus AZ has been "Spending like California" for about 10 years now. That has consequences. One of the consequences is that the State has radically cut back state funding to the municipalities and counties. (a lot of city and Co. funding is a transfer from the State of AZ).
The good news is we have only been doing so for 10 years, while CA has been doing so since Brown was Governor.
Basically half of the Co and City budgets went *poof* after the state actually started trying to balance the books, and they ain't balanced yet. We still have another 2-billion in spending we need to eliminate.