Sin tar is the usual way, though it’ll sometimes come out more sin tawr, where the au is a bit more drawn out.

Sin tore is a fairly common one.

However, sin tar is more common, at least with what I’ve heard in meat space. That’s a fairly limited thing though, since most of the people I have talked to over my fifty years have been fellow southerners. We do tend to use softer vowels in most cases, and tar is softer than tore in the way we tend to do vowels.

However, with the latin and Greek origins of the word, I’d argue that the tar or tawr would lean closer to that than tore, just because of similar words. When an au is present in medical terminology (which is where almost all of my latin and Greek comes from) it usually gets pronounced aw or ah, not oh.

But, I never hear anyone pronounce the initial C as a K, and that’s the way it would have been in both of those languages originally. The Greek version is spelled with a K, when written with the usual alphabet rather than Greek. Kentauros.

Which is an aside.

Wikipedia lists the two I did as the usual pronunciations, fwiw. And all the dictionaries with audio options are either those two, or slight variations of them, where the au sound is rounder or flatter than the norm.

Thing is, it’s a word in a living language. Whatever the original English pronunciation may have been, that can change, so supporting a pronunciation is kind of meaningless. What matters is consensus over time, and by location.

So, a regional accent that sounds more like cent-ur is just as valid in that region, it just isn’t standard. So would any other variant be, if there’s enough people using it to be called a consensus.