DEERFIELD, Ill.--(BUSINESS WIRE)--Walgreen Co. today announced that December sales increased 10.2 percent to $7.92 billion from $7.18 billion for the same month in fiscal 2014. Total front-end sales increased 3.5 percent compared with the same month in fiscal 2014, while comparable store front-end sales increased 2.6 percent. Customer traffic in comparable stores increased 0.3 percent while basket size increased 2.3 percent. Prescriptions filled at comparable stores increased by 7.8 percent in