Another option:
Most cops wont bother you if you are driving 70 in a 65. But lets say you travel 70 miles per day to get to work.
If you went 70 miles per hour instead of 80 miles per hour it would take you an extra 7.5 minutes to get to work every day. If you set your alarm 10 minutes earlier each day you could still get to work the same time and have a few minutes to spare (get a coffee on the way).
The money you saved on not buying all the speed equipment, radars and shit would pay for free coffees every morning. Cool? Something to think about anyway.