In my experience the likelihood that your luggage will be checked is minuscule and usually when that happens German customs agents are fairly reasonable.

In the cases where I brought wrapped presents that were above the customs free limit (430 Euro; see http://www.iatatravelcentre.com/DE-G...ils.htm#Import regulations) showing receipts was fine. In this case you will have to pay a tax of 19% plus, depending on what you bring, the import duty.

However, if you have a fancy wrapping it will probably not survive the trip in your (hand)luggage anyway, while if you have a simple wrapping, why not carry the wrapping paper separately and then wrap before giving the present?