Thank you very much.Not if you live in Victoria. I think you could probably get away with registering her as SBT x Cattle dog or something - stay away from Amstaff on the rego form because they will want proof.
The Victorian local government do not accept DNA tests as proof of breed either. You've got a good chance of getting back "significant Chihuahua" if you do that - doesn't take much for some really weird results to come back on the DNA tests. So not really worth $150 except for the entertainment value. There's a few youtube clips of people with their dogs reading out their bizarre DNA results.
The most important thing you can do with a scary looking dog - is make sure she never escapes. So if you're expecting tradies - make sure she's secure. And make sure the gates or doors to your house are locked so stray people can't "accidentally" let her out.
When I first got my dog and she was all cute puppy - I took her on a tour of my neighbours - knocked on their doors - said this is my dog - any problems come to me first... so they know I'd be willing to listen and hear them out instead of some people who get angry and abusive if you have a problem with their dog. Some neighbours won't take the risk and they just call the council.
Council can't come into your house and sieze a dog without your permission or a warrant and police (you get some warning). They can go into your back yard and seize a dog without your permission and without warning or you being at home. And that can happen if someone says you have a pitbull. They just go by looks. If your dog is registered with a plausible breed id cross - they may accept that and leave a note in your letter box.
When I'm out, my dog stays in my house.