+1 it's a myth. Firstly, he number of coins required would be more than ever existed in the history of 5 cents.
Secondly, apple could decline payment because of legal tender eg in the UK, you can lots of 5p coins up to a value £5 and it's legal but after that, it's no longer recognised as legal tender.
Thirdly, the number of trucks required would be about 3000 and not 30.