For RMS licensing, there are single-user dongles available. If you will only have one POS station running, that's all you need. Manager stations do not require additional user licenses.
As for SQL licenses, it is the number of concurrent connections that will determine how many CALs you need. However this only applies to the full-blown SQL Server product. MSDE (Microsoft SQL Developer Edition), which is what is included with RMS, doesn't have CALs, so you can have as many copies of Manager running as you would like. You only really need the full-blown SQL Server if your database will be over 2GB in size, and you can buy that when the time comes.