I have only worked on that model a few times but I remember that you need system flag tables to set things like decimal point position. Look under system flags in your manual and you should find one of the flags controls the number of zeros before and after the decimal. If you have lost the manual, one of the users has one here:
http://the-checkout-tech.com/manuals/cashregisters/Towa_FX-400_and_Geller_FX-400_operating_and_programming_manual.html
Registerman, October 2013
