How do I get a federal tax id number to buy wholesale?

I am wondering how I go about getting a federal tax id number in order to buy wholesale. I am a crafter and although most of the items I make, I give away, it would be nice to have a tax id number in order to buy supplies wholesale. I would only sell the occasional item so I don't know if I need a resale... show more I am wondering how I go about getting a federal tax id number in order to buy wholesale. I am a crafter and although most of the items I make, I give away, it would be nice to have a tax id number in order to buy supplies wholesale. I would only sell the occasional item so I don't know if I need a resale license or not. Also, if I have a federal tax id number, does this impact the way my taxes are filed for my "regular" job? Is there a downside to having an id number if I am not going to turn a profit?
Update: Just to clarify, I am not looking to get out of paying sales tax, I think I will sell so few items that it won't cost much. What I am wanting to know is what kind of id number do I need to buy wholesale (i.e. not at a mark-up) and how do I get one.
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