The standard fee to cash in coins at a Coinstar kiosk is 9.8%, which I think is way too high, and you should explore other options for depositing loose coins. However, if you redeem for one of their gift certificates there is no fee, and there are often promotions that make it even better.
From 8/27 to 9/23/12, if you pour in $20 of coins and redeem for a $20 Amazon.com gift certificate (no fee, good for anything at Amazon), you’ll get a free additional $5 code good only for Amazon MP3s. The code prints automatically on the bottom of the receipt, so if have a lot of coins you can break them into $20 increments and get multiple $5 Amazon MP3 credits. That’s not a bad deal if you shop at Amazon regularly and also like digital music. The bonus code expires 10/31/12.
I still prefer getting my coins deposited at my local bank with no fees, as I can get 6% off any Amazon.com gift certificate anyway with my American Express Blue Cash Preferred which gets 6% back on anything bought at a grocery stores – including gift cards. If you have a rewards card with a grocery bonus, don’t forget this option when buying gift cards.