You have a few choices.
if you have a previous version of ms-access, then you can
purchase a new copy for $109.
Full retail price is $229 if you don't have a previous version
..
You could also consider purchasing one copy of ms-access, and then using the
runtime packaging system.
Right now, that system quite expensive..but, certainly a bit less then
purchasing 5 copies.
Note that for a2007, the above pricing should be the same, but the runtime
distribution system is going to be free.
That runtime system allows you to package your appcation on a disk, and it
can be installed on any windows box..including those without ms-access.
I don't think any type of volume licensing for ms-access is availing for 5
copies..but, I think 10 copies is a possible starting point.
If those users actually don't need ms-access, but ONLY need to run an
application you built, then he runtime system would make sense if you need 5
or more copies....
If you have an existing version, (a2000 to a2003), then presumable you could
upgrade to a2007 for $109, and then distribute the application to all
machines for additional zero cost per copy. However, the problem is that the
runtime and package wizard stuff is not yet released for access 2007.