If price is 45p and people give 50p and want no change, how do I do books?

This happens in the charity I have started being a bookkeeper/treasurer for. What do I do with difference as revenue is always much higher than axpected. Sonetine it is becaue people do not write down thwie sales (They don’t like using a till)
and sometimes it is becuase people say keep the change.

How do I recognise this in the books? I was thinking of putting a column just for donations? Is this OK?

Will these donations qualify towards GIFT AID? It is too small to be VAT registered.

Do the accounts have to be prepared 10 months after year end? To companies house (UK)

Any other tips for me?