NC has higher gas taxes than any other state in the south. Lower gas prices in VA and SC all the time, due to lower taxes in those states.
One major reason prices are low is that the dollar is very strong. Petroleum is priced in dollars, so when the dollar is strong the price goes down. And vice versa.
Since my salary depends on that gas tax, I need to point out that North Carolina does not have any county-maintained roads, so that unlike in other states, no county property taxes go towards transportation maintenance or construction. The municipal costs are also reduced compared to other states because a portion of the gas tax revenue is directed to municipalities (this is called Powell Bill money.) All public roads outside of municipal limits are state roads, and most major routes inside municipalities are as well.
It is one example of why just comparing basic tax rates does not accurately compare overall tax payments per state (or municipality.) There are web sites out there that do that. (Anything more and I'll get into PP territory!)