Fuel sales decreased 5.4% on the year in January through June, data adjusted for the number of working days and seasonal factors showed.
However, sales of non-food and food items were up 2.3% and 0.5% on the year, respectively.
In June alone, adjusted retail sales were flat from a month earlier, but fell 2.3% compared with June 2012.
In unadjusted data, retail sales inched down 0.9% on the month in June and were down 4.2% compared with the same month of 2012.