Currently, items that are added into the Cash Donations category are excluded or 'hidden' from the online auction website but still remain in your Item Management.
First, make sure the 'Cash' category is available for your items. To do so, go to General Setup > Item Categories > Select Cash
Next, go to Items > Item Management > Click on the item to edit and change the category to Cash > Save the item
In order to make the item viewable on your auction site, change the category of the item back to the category of your choosing.