I really like this Coin Jar! However, I think it would be improved by moving money such that the balance on the main account is whole pounds rather than the price of purchase. At the moment my balance ends in .17, and as far as I understand will continue to do so forever unless I transfer 83p into my account, or run my balance to below £10 and somehow manage to spend 17p before I top up again. (This mildly offends my sensibilities.)
I think my suggestion is similar to the Precise Coin Jar that Simon suggested.