Speed Limit Cushion?

What is the name of your state?
Ohio - Franklin County - City of Columbus
AND
Missouri - St. Louis County - City of Clayton/City of St. Louis (Where I go to school)

I was wondering if there is any sort of cushion or grace area where the cops will not pull you over for speeding. I can be a very uptight person about certain things and driving is one of them. Driving down highways, I usually set cruise at 63-65 in a 65 zone and 53-55 in a 55 zone. My questions is that when I'm doing this, I always seem to be the slowest car on the road and I never pass anyone except trucks. How do so many people break the speed limit and get away with it? There must be some sort of unofficial cushion right? Especially in the 55 zones in downtown areas or construction areas, when I go 55, everyone seems to be doing at least 60 including some truckers! I am an EMT in traning and in the driving part of the class we're taught that even going 10 over the speed limit will save you 2-3 minutes at the most going across the city but increases your accident chances by 50-100% so it doubtful that I will take advantage of this cushion if there is one, but it would be nice to know if one exists so I'm not freaking out everytime my cruise goes to 66 and i see a cop!

Thanks guys!
-Wu

What you're asking isn't exactly a legal question, as an officer could indeed give you a ticket for driving only one mile per hour. What these speeders know is that there aren't enough cops to watch the entirety of the road, and the few cops they may pass have likely already pulled over somebody driving faster, and thus are too preoccupied to pull them over. Some drivers are of the ilk that believe as long as they are "going with the flow" or "driving with traffic" that they can avoid being singled out and pulled over, but reading some of the posts on this site can show that that isn't completely true. So to answer your question, nobody knows; depends on the location, the time of day, and the officer that spots ya.