How can I change, add, or remove information displayed on a register receipt?

At the top of the register receipt, is the Receipt logo and receipt header. 

Just below the receipt header, the following is listed...

1. Current date and time (ex. 5/22/13        12:28PM)

2.  Four digit transaction number and 5 digit Store id   (ex. Trans.:  7546          Store:  4147)

3.  Register and Till id  (ex.  Reg.:  242     Till.:  081)

4.  Cashier and Sales id  (ex.  Cashier: 123456789    Sales:  123456789)

5.  Transaction barcode

How can I masked the first few characters of the Casher and Sales id?  (ex.  Cashier: 123456789    Sales:  123456789)  would be displayed like (ex.  Cashier: xxxx56789    Sales:  xxxx56789)?

How can I hide the Casher and Sales id?  (ex.  Cashier: 123456789    Sales:  123456789)  would be displayed like (ex.  Cashier:     Sales:  )?