A convenience store and gas station chain has more sites under contract in the Miami Valley. Casey's General Store (NASDAQ:CASY), based near Des Moines, Iowa, has been targeting small towns in the Dayton region and now has sites under contract in Tipp City and in Jackson Center. The Dayton Business Journal previously reported the convenience chain also has locations planned in New Lebanon, north of Greenville and in Fort Loramie, which is in Shelby County. Casey's General Store bills itself as…