Honolulu gas prices followed a nationwide trend last week, landing at $3.30 on average for a gallon of regular as the three-day Independence Day weekend ended, according to GasBuddy.com. That was a half-cent a gallon less than the week before and a nickel more than a month ago, said GasBuddy, a website that tracks 214 retail outlets on Oahu. Oahu motorists were paying an average of about $1.02 a gallon more for gas at this time last year. Nationwide, motorists were paying an average of $2.77 for…