When creating a new site, the site structure can be of some benefit for ranking.   A site that is divided into logical and clearly demarked sections can help the visitor navigate your site and help the search engines figure out what your site is about. The specific urls can be a good guide. If your site is large, then use folders and sub-folders that are appropriately named with keywords, along with the page file name. By doing this you will end up having a url laced with keywords.

For example if your site sells “pet supplies” then a good domain name would be www.pet-supplies.com If you sold pet food you could have a directory called “petfood” . Then you might be selling dog food or cat food or bird food so your url structure could look like this:

www.pet-supplies.com/petfood/catfood.html and www.pet-supplies/petfood/dogfood.html.   By structuring you r site this way, you are creating urls give a lot of information to your visitors as well as the search engine.  

If you are considering different ecommerce packages to build your ecommerce website, a solution that lets you easily name your urls to logically mirror your category, subcategory and products, will give you a slight advantage over the site that does not.