Petro prod mktg co needs eCommerce Sol

Hi there!
One of my clients, a petroleum product marketing company with its own gas-stations and other Petro products with a network spreading over a region as large as California, needs an eCommerce solu for its POS/Sales/mktg and distribution. Wealso need to develop the feasibility of the project, we are thinking of ERP based sol. Thank you for your advice on the matter.