Retailers say Missouri’s experiment with a tax-free weekend proved very profitable for them. The state didn’t charge sales tax on back-to-school items this weekend, saving shoppers a bit more than 4% on certain purchases. The savings grew in those communities in which the city and county participated and didn’t charge their sales tax.Missouri Retailers Association President, David Overfelt, says retailers in those communities which did charge local sales tax, had a tough time calculating the sales tax owed. Overfelt says those local governments that opted out were short-sighted, because they failed to back their retailers against those selling via catalog or Internet, which he says is the real competition these days. Overfelt says the association will be getting some hard numbers from retailers this week. He says his assessment of the weekend comes from informal discussions with association members.