Next time you pump gas, please do yourself and environment a favor by not topping off your tank. I read from an article that these few extra clicks can not only compromise pump's vapor recovery system but your health.
The vapor recovery system, when working properly, creates a seal between your car and gas nozzle to capture and store underground 95 percent of toxic gasoline vapors. But when you top off, the gasoline you think you are pumping into your tank gets trapped in the hose or in the rubber boot of the nozle. The spillage have a big impact on the environment since it gets seeping into the ground and water supply and releases vapor detrimental to the environment and your health. Exposure to such dangerous vapors as benzene and toluene adversely affects the lungs, kidneys, heart and central nervous systems.
So please refrain yourself from the tempetation of rounding off your sale when pumping. It will do so much good for the environment and your own health.
***I'll be watching you***