iTunes Computer Authorizations: Multiple Users - One Authorization for all?

So, this may be a dumb question and I have tried to find an answer to no avail. I am wanting to set up iTunes to use the same information for all three users on one iMac. I am hoping this will include the iTunes authorizations (which are limited to only 5 total).

Is this possible? What I don't want is to have one computer (with three users) use up over half of the authorizations on one machine. If it is possible, can anyone direct me to instructions on how to set it up? Right now iTunes set up for one of the users.

Thank you for any help you can provide.