I don't know how much this can be controlled, really. My only
suggestion would be to create  one top-level sales  site, and create
subsites within that site  collection. The url's would then read
http://servername/sites/sales/sitename

probably not the best suggestion but that's all i have for now...

If you want to add more options like the "sites" you should navigate to
the Windows SharePoint Services Admin page, and find the Virtual Server
in question. From the admin page of the Virtual Server go to the
"Managed paths" - I am not sure of the naming, as I am testing it with a
Danish edition - from here it is possible to add more managed paths.
Look at the configuration of "sites" to see what settings you should
apply.