Taxing sugar is not an incentive to sell more nutritious food, unless we're taking those taxes and subsidizing produce with them. Those sweet, highly-processed foods are also a way better purchase for grocery stores, which don't have to worry about the food going bad before it's purchased.
I do think banning these types of stores is likely to cause more harm than good, though. To take it to extremes, there's simply never going to be a farmer's market where my closest Dollar General is.