Re: Er ....
Well, at least the states could harmonise their own code internally rather than leaving it to be decided at county level.
That's not going to happen for the same reason states won't harmonize their taxes -- local control. People like being able to vote on exactly how they'll be taxed.
Some counties choose to use more property taxes, others more sales taxes, still others user fees and personal property taxes. In some states cities can also charge their own income taxes.
What fits best tends to depend on where the revenue comes from. Soaking tourists with a high sales tax is a popular option for popular destinations. Counties that border states with no sales tax probably won't want to charge a high one, lest everyone just go across the border to shop.