This is a totally subjective realm of thought because it has way.... too many variables to give a clear cut answer.
My department "usually" allowed a 10 way give or take, unless it was an obviously stupid or disrespectful driver, or an impaired or suspect driver. Now the variables start becoming, is it an enforcement task force (very little tolerance) or a check point or is the officer having a very good day or a very bad day, are you being a dumba** on his roads etc.
I can tell you, with rare exception if our unit had the word "traffic" on the marked unit you could plan on a "press hard, five copies" if stopped.
I have many friends who proudly serve as Troopers on the highways and most will say something similar to the above but please keep in mind an officer is allowed nearly total discretion in a speed violation and will (and should) use their judgement.
Now with that disclaimer having been said I'll honestly tell you I generally will run (other then those sudden bursts, totally caused by my Vette) no more then 10 over.
Their are several present members of the forum who are, or were LEO. See what the guys say.
Oh and as a final note beware of small towns!
Ken:thumbsup: