With the rise of virtualization, the share of e-commerce in the retail market continues to grow in an omnichannel context. We consider an existing software tool, developed by the Devatics company, for pooling inventories in stores to meet online orders. The problem which arises therefore consists in seeking the optimal allocation of a set of customers to stores. In this paper we consider a variant of the offline problem corresponding to an evolution of the existing software, consisting of assigning a set of predefined orders when the transportation cost depends on a delivery tour to the customer locations. We show that the problem corresponds to a vehicle routing problem with additional but standard attributes. A mixed-integer linear programming formulation is given and several heuristics are proposed : a giant tour-based genetic algorithm, a simple cluster-first, route second heuristic and an assignment-based genetic algorithm. Preliminary computational results on a set of realistic problem instances suggest that the assignment-based genetic algorithm better scales as the problem size increases.