Taxes would be based on fair market value at the time of the transaction. There are policies around this already, otherwise the rich could avoid taxes by bartering with cars/watches/paintings.
Sounds like it's just making work for the IRS. I'm curious if the situation is the same in Australia. Can't find anything definitive online, though I've never heard of a business here taking payment in anything other than AUD (except at the airport, where many retailers will accept other common currencies).
Is it similarly legal (in the US) to pay workers in "alternative" currency-substitutes?