After a slight increase, gas prices across the nation have started to fall again. According to GasBuddy.com, the national average for a gallon of regular gas is $3.37. In South Dakota, the average is a penny less with a few Sioux Falls stations selling gas for less than three dollars. GasBuddy senior petroleum analyst Gregg Laskoski joined Dakota Midday and said gas prices are falling as stations switch to cheaper winter blends this week.