The normal Tax Rate give me an Aproval of 72%, if I hover over the medium Tax the Tooltip shows "modifies Aproval by -12%".
It actually give -30% Approval.
It´s the same with all higher Tax Rates no issue between Low and Medium.
Citizen: Normal Tax: no complain about Tax Rate!
Medium Tax: -30 Aprova Cause of to high Tax rate
To reproduse start a new game and take a look at the Civ screen
Version: Beta .071.275314