as said above, ight click on a unit card and click on abilities. it should say policing bonus or something like that. it will say that on dragoons and some others (i havent played anyone except russia and marathas, but russia has the melee axemen with policing bonus)

if you want to raise taxes but only 1 region is against it, recruit some policing bonus units and then raise taxes. dragoons cost 600-something, but i have russian melee infantry that give the same bonus for only 380.check prices and location first. if you have a city tuckded far into the middle of your empire, then you shouldnt need much more than a few units of cheap policing units. but if you have a city you just conquered way out in harms way, garrison it with standard military units and dragoons. then if it is assaulted it can hold off, but still haev a policing bonus.