会计 instead of 收银机，现金出纳机, cash register?
In this context, 会计 refers to the person who is doing the accounting job, that is, accountant. 

Most of time, 会计 just refers to accountant, as in: 她是个会计. 

会计 can also refer to the job for accounting, as in 会计学，会计师，会计协会，etc.