Wal-Mart Stores (WMT) increased the share employees pay for its medical coverage programs 8% to 36%, depending on hours worked and pay, saying it expects health costs to continue rising . Like other large employers, Wal-Mart is trying to manage costs while at the same time preparing to meet strict rules mandated in President Obama's health care overhaul, commonly called ObamaCare. Wal-Mart, the world's largest private employer with some 1.4