You would not be liable for a fine (If you think about it, how can you be - Australia does not have jurisdiction over you as you are in New Zealand, and you have broken no NZ law - Further, you declared the item to customs so even in Australia you could not be held liable)
Looking at it another way, if you had gotten on a plane with it, declared it to customs on the arrival card, they would have simply asked to see it and made a decision whether to let it in or not - they would not fine you.
Customs may or may not confiscate it (ie they may let it through). I've not sent a parcel to Australia, but I have imported seeds into NZ - I made a number of calls and emails to ensure I got the process right - expected to pay quite a lot of money to do it - in the end they just came straight to me - MAF did not even examine the parcel.
Being that NZ and AU are pretty similar in terms of legislation (ie both the food standards are the same) - its probably actually Ok to send it anyway - in fact the Imported Food Control At 1992 - which I believe is applicable - specifically exempts many foods imported from New Zealand from the act.
The last paragraph of this AU government web page states "The only New Zealand foods that are subject to the IFIS at the border are those classified as risk foods. Equivalence determination of food safety systems covering dairy products was reached in 2007 and seafood, uncooked pigmeat, chicken meat, coconut, pepper, paprika, peanuts and pistachios were aligned in 2011. This enabled these products to be brought under the TTMRA and removed the requirement for border inspection for these products."