with things like that, it really depends what people say to you first, as well as the situation, to me they all mean the same. Really depends on what you think is comfortable. What do other people think?
Thankyou, you would say: You welcome ( that seems to be more formal too)
It doesn't matter. ( not too sure on that one)
Never mind. ( I personally don't think you use that when ppl say thankyou to u, I wouldn't )
That's all right. ( when you have done a small favour, more slang)
Not at all. ( I think only chinese ppl use it, I have never heard any european ppl it)
Other common ones are :
No problem/ No worries, that's all I can think of now