I have been to more one fast food type restaurants that have signs saying they don't accept 5c coins, today another one trying to tell me they don't accept 5c (verbally, no signage). These are all cash businesses, otherwise I always pay by card. In all cases I left the money on the counter and turned around, ignoring what they say because 5c is a legal tender, I accepted it as change from others and I expect others to accept it as form of payment.
It prompted me to look up the conditions of payment in coins:
http://banknotes.rba.gov.au/legaltender.html
- not exceeding $5 if any combination of 5c, 10c, 20c and 50c coins are offered
- not exceeding 10 times the face value of the coin if $1 or $2 coins are offered
If someone wants to pay a merchant with five cent coins, they can only pay up to $5 worth of five cent coins and any more than that will not be considered legal tender.
So a merchant can't just put up a sign and refuse to take 5c coins unless in excessive amount. I found it is a very poor customer service practice, they can easily change the 5c at the bank as they have to go to get changes anyway.
Additional info
Further reading indicates a merchant can specify accepted form of payment in advance, for example not accepting 5c coins before exchange of goods.
Nice Find!