Actually if you are providing services good enough to get residential/orifices to max level you can increase taxes with no real downside. Assuming of course you don't go crazy with it. I usually end up at 11 or 12% once I have all services built up in a mature city.
Once all my services are built-up in my mature city, I find that I usually can get away with 12 and 13% tax rates.
Citizen Happiness seems to be a good indicator/clue on what rate you can get away with (Click the Info Views button, then Citizen Happiness).
If Citizen Happiness is in the 90 percentile range, you can set this group at a tax rate of 13% (in my city, this is Office and Industrial).
If Citizen Happiness is in the 70 percentile range, you can set the tax rate at 12% (my Commercial).
My overall Residential group is in the 70 percentile range. But my (sub-group) High-Density Residential (HDR) must be slightly "happier" than my Low-Density Residential, because I can set my HDR tax rate at 13%, whereas my LDR must stay at 12%.
This could mean that Citizen Happiness in the 80 percentile range, can also accept a (higher) tax rate of 13%.
Note: I'm not positive if there is an actual and direct correlation between Citizen Happiness and tax rates, but it seems to make some sense in my city's situation.