The official App Store and iTunes Store policy is that all sales are final. There are a few exceptions to this rule. You can get a refund if the app crashes or does not work, if you are charged but do not receive the item (including in-app purchases), if the app is not compatible with your device, if the app does not work as described or is otherwise a scam.
Deleting an app will not refund it. The proper venue for getting a refund is described below.