I wish americans would stop saying "I can/could care less". I know that's how it gets said most of the time on american tv, but it's the opposite of what you actually mean.
You want to say 'It doesn't mean anything to me/It doesn't matter to me/I don't care about it' etc.
When you say 'I can/could care less' - that means that there are things you care less about than this - which means you do care about this in some way.
The correct expression that means 'I don't care about it' is - "I can't/couldn't care less' - meaning that there is nothing at all that you care less about than this thing