To change prices on a group of items and one time, choose Pricebook Management and the Manage Pricebook:

Once inside the Pricebook do a search for what you are seeking, such as Department = Candy. Then, sort the description column and hold the CNTRL key on your keyboard to select multiple items, for example Tic Tac:

Then, right click to change price on selected items:

Click OK and then click the SAVE button at the top of the page to send items to POS.