Point of Sale

I own and operate 2 brick and mortar stores, one warehouse that receives centrally and fulfills ecommerce orders. I need a robust point of sale system that will seamlessly integrate all functions and inventory from all locations with the warehouse as head office. The ecommerce must use the inventory from all 3 locations in real time, or in set time increments. Website must be user friendly in regards to order-fulfillment, look & feel, and merchandise placement. I am not sure what infrastructure is needed. I am willing to listen to suggestions. Good communication is required. Samples of related projects also required.