I've noticed that bushes, books, torches, and so forth only ever drop solid colored coins: copper 1cr, silver 10cr, and gold 50cr denominations.
Not once have I seen, in person or on YouTube, or even heard tell of a copper-silver 5cr or a silver-gold 25cr drop from a bush or other destructible.
Is this a bug or has it been confirmed by a dev as an intended feature?