A POS-based checkout/scale system including system housing having a vertical housing section with a vertical scanning window, and a horizontal housing section. An electronic weigh scale subsystem is integrated with the system housing, and has a weigh platter supported above the horizontal housing section by a pair of cantilever-type weigh scale arms operably connected to an electronic load cell module. During a first mode of operation a powered support mechanism allows the cantilever-type weigh scale arms to bear the full weight of the weigh platter and any items supported thereon so that the electronic load cell module can accurately measure the weight of items on the weigh platter, and generate weigh data for transmission to the host computer system. During a second mode of operation, the powered support mechanism automatically prevents the electronic load cell module from experiencing the weight of items placed on the weigh platter.