The present disclosure is directed at systems, methods, and apparatus for precisely inventorying items placed within a user-portable container. The system may comprise one or more interrogators configured to repeatedly send interrogation signals to detect tagged items placed within the portable container by a user. The system may also comprise one or more readers configured to detect response signals produced by the tagged items in response to the repeated interrogation signals. The system may also comprise a communication interface configured to provide information regarding the detected response signals to an adjunct processor configured to analyze the signals and determine whether they originate from items within the user-portable container, as well as to maintain an inventory of items within the portable container.