The latest CSO figures shows retail sales last month fell slightly, by 0.2%, compared to the previous month.
And sales decreased by almost 1% during the past year.
The motor trade saw the biggest monthly decrease, with sales down 4.4%.
There were also falls in sales in clothing, footwear, textiles, hardware, paints and glass.
But furniture, electrical goods, books, newspapers and stationery all saw an increase in sales.