royal alpha 587 cash register manual?

This model is not supported any longer I would say, so you are unlikely to find anything for free. C-tech has the only full manual I've seen. It has the system clear information which may work for your problem.
The manual is here:

http://the-checkout-tech.com/manuals/cashregisters/Royal_Alpha_587_operating_programming_manual.html

Registerman
November 2010