After you fail to turn up to tick your name off, AEC will send you a letter asking why you didn't vote and if you have a legitimate reason or not. They state on the form that if you don't have a legitimate reason, they will fine you, but the first letter that comes isn't a fine, just a please explain. On that form, you write in your reasoning, I forget the exact scripture but I quoted the bible after researching why Jehovah's Witnesses don't vote, and made it sound schizophrenic as well. I didn't get a fine, and next time I failed to vote, they sent a second letter and again, I claimed religious reasons for abstaining, and after that they have never contacted me again. They seem to take religious exemption at face value without investigating further.
I have no outstanding fines, am able to register my car, renew licence, renew passport, go overseas, never received any enforcement notices, so I assume at some point they automatically mark you down as exempt. I don't know if they remove you from the electoral roll, but I have never been bothered about failing to vote for local, state and federal elections in roughly 10 years. I know some people are happy to just mark their name off and dump their vote, but I'm not willing to waste my weekend mornings standing in line to do that shit.