To select which items have prices tags and which do not, firstly access the Item Details screen by clicking 

MENU - ITEM - ITEM DETAILS

Find the item that you need to alter and click the edit button: 

If you want to NOT print a price tag put a tick next to Tag Supress Print, if you want the item to print a price tag, make sure the box is UNTICKED:

Don't forget to click the UPDATE button at the bottom of the screen once you have made any changes.