Is there a “proper“ way to say “6:05 AM”?

I noticed that I and Alexa say “six ‘oh’ five a m”, but is that the correct way of saying the time? Specifically the “oh” part?

Kind of like when speaking out a phone number, how we might say “my number is one two three, six ‘oh’ six…” but really, that’s not an “oh” like the letter O even though it looks like an O, but everyone knows the person is saying “six zero six”, which is the proper way of saying that.

Edit: thanks for all the answers everyone! This was just pure curiosity for me but I really enjoyed reading everyone’s responses and learning some new things!