WHY 9/10 OF A PENNY ON GAS PRICES?Rick Rock
Why 9/10? It's the one thing that is consistent where gas prices are concerned but why does the price always end with nine-tenths of a cent? Because it makes consumers feel better. So, although AAA's national average price is now above $5 a gallon for the first time on record, the most common price for a gallon of regular gas is still at $4.999.
Source: Northwoods Petroleum Museum, Wisconsin