ALTOONA, Pa., 2016-Dec-07 — /EPR Retail News/ — Sheetz, one of America's fastest-growing family-owned and operated convenience retailers for more than 60 years, today (Dec. 6, 2016) announced the upcoming openings of three new stores in central Pennsylvania:  Manheim, Hummelstown-Derry Township and York. The first opening is scheduled for Thursday, Dec. 8 at the store in Manheim,…