Yes, you can, click on Help, Seller's Guide, Managing your auction & you'll get this:
Ending Your Listing Early
Sometimes something goes wrong and you can't complete your listing as planned. If needed, you can choose to end your listing before the scheduled date. If there are bids on your item, you can cancel them.
Reasons for ending listings early include:
The item is no longer available for sale.
There was an error in the starting price or reserve amount.
There was an error in the listing.
The item was lost or broken.
"To end your listing early, follow these steps:
Type your item number into the Ending Your Listing Early form. (You can get this number on your listing, on your confirmation email, or on your My eBay page.)
If there are bids on your item, choose between:
Cancel bids and end listing early
or
Sell item to high bidder(s) and end listing early
If your item has no bids, you'll skip this step.
Choose the reason you're ending your listing early.
Now your listing will end and will no longer be displayed on eBay. If there were bidders, they will be emailed that their bid was canceled and the listing ended early. "