Yes. it does.
Australia Post itself doesn't take weekends into account, but the ozpost servers do. (also public holidays).
About the only difference between TNT quotes and the Australia post quotes is that quotes made after 3pm will have an additional day added.
These estimated days really are only estimates. Other than TNT (which is quite specific) Australia Post and all other couriers have a ~2 day window. The ozpost servers ensure that estimated deliveries won't occur on weekends. (Saturday or Sunday postage is "permitted" for Australia post pre-paid products)
Cheers
RodG
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