E5 means no clerk logged on. Your machine is set to have staff log on before you can use the machine. If no one has changed the default log on codes, then you should be able to press CLEAR then 1 then ID button to log on as person 1.
E6 is a general error. It is basically saying wrong input so still related to logging on at this stage.
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If anyone needs a Towa / Geller AX-100 manual, go here:
http://the-checkout-tech.com/manuals/cashregisters/towa1.php
Registerman, July 2010