[Pocus]

you can go up to 130%, which costs you 0.9% of total population each turn. If you lay down the figures on a spreadsheet, you will see that doing this for 3-4 turns is worthy of interest for the extra gold taken, but only if you happen to have units standing by in the provinces and not dedicated patrollers (eg waiting for an army of sufficient size to be gathered).

Note also that growth is not that bad in this respect, as you get +0.6% growth for the +3 scale, compared to say -0.6% for a 120% tax rate. On a maximized econ (250 gp roughly in your home province), thats net you 50 gp more a turn without change on your population. Your initial army can handle the 3-4 pts of unrest w/o problems too.

So to disgress a bit : order 3 give +21% gold income, and growth 3 +26% gold income (+20% from taxes, +6% from scale). Growth is not that bad in places where you can patrol for the extra taxes.