Retailers that cater to discount-conscious consumers are thriving, and so chains like Five Below Inc. and TJX Cos. are making hay while the sun shines, opening about 100 new stores each by the end of this fiscal year, according to Coresight Research. No other retail sector, however, is experiencing a growth surge like big dollar store chains, which are leveraging the ability to serve exurb areas around the country. Dollar General and Dollar Tree combined say they will open over 1,300 net new locations by the end of their fiscal years in January.