If you live in Georgia the state only tacks on 7.5 cents per gallon. But in Connecticut it's a whopping 36 cents per gallon. Harold mentioned an eleven cent difference in price between Iowa and Missouri. Iowa's state gas tax is three cents higher than Missouri. County and city taxes could make up part of the difference.
Many environmentalists favor even higher taxes in an effort to reduce consumption of gas.
Pretty hefty when compared to most sales taxes. The other large component of gasoline prices is the cost of the crude oil used. The United States consumes an average of about 20 million barrels of oil per day. But that average masks wide swings in price. So it's not surprising that gasoline prices are up.