Just had a look for a programming manual but realised this machine is 11 yrs old!! I have dumped a lot of the older ones now. This manual at C-tech is an NX-5400 01 type but it should be the same for programming PLUs:
http://the-checkout-tech.com/manuals/cashregisters/Uniwell_NX-5400_type_01_programming_manual.html
Registerman, May 2012