That's a very good question, Austin!!
As Ryota mentioned, The correct way to write it is "こんにちは". Nowadays even some Japanese people use "こんにちわ" and I think that makes Japanese learners confused. It may be used amang friends, but it's not grammatically correct. Just a slang word. Like usage of "Anyways" in the US, I guess?? I hope this helps.:)