CHESAPEAKE, Va., 2015-7-17 — /EPR Retail News/ — Dollar Tree, Inc. (NASDAQ: DLTR), North America's leading operator of discount variety stores, announced today that Michael Witynski has been named Chief Operating Officer. As Chief Operating Officer, Mr. Witynski, age 52, will be responsible for Store Operations of Dollar Tree bannered stores in the United States, Real Estate for…