Each has a point of entry, traffic routes and a point of exit. It matters little if the general purpose of the site and the grocery store are the same. Both are trying to convey a message and to guide the consumer along to make considered decisions. Both are operating in interactive media. One is virtual and the other is not, but results can both be substantial.
Lets review the grocery store design basics.
The consumer has to follow a pattern in order to become active. So too must those who come to your site via the Internet. Men are predators and can enter, acquire, pay and leave but women like to graze and spend more time inspecting, reviewing and at times socialising. If you can add a social character or personality to your site they will become much more compelling. The decision where to shop is often based upon loyalty which is based on trust, perceived value, convenience, selection, quality and security.