From ebay pages :

[reason to cancel]
"You want to end your auction early because you no longer want to sell your item.
In this case you must cancel all bids on your auction before ending the auction."

"Because your cancellation will be put in the bidding history for this auction, bidders may ask you to explain your
cancellation. So, please include a one-line explanation of your cancellation for the official record."

Cheers,
Y.S.

PS: I am not sure why you have to cancel bids first : don't
realy see what it change. But well...