In short, the U.S. Mint allows you to buy rolls of $1 coins at face value with free shipping. They come in boxes of 250, and individual orders are limited to two boxes ($500). There doesn’t appear to be any restriction on the number of orders that an individual can replace, but you might want to keep a relatively low profile when doing this so as not to raise any red flags.
Here’s the scoop straight from the Mint:
For circulating $1 coins you want to spend or use in your business operations, we offer the Circulating $1 Coin Direct Ship Rolls. You can buy up to 500 $1 coins at face value and receive free standard shipping and handling.
So you’re effectively just turning your turning your credit line into cash with no overhead cost. Of course, the U.S. Mint has to eat the credit card processing fees, so it’s not exactly a victimless crime (so to speak).
Here’s the link to coins. Unfortunately, they’re currently sold out. But if you’re interested in trying this out, keep an eye out as they’re bound to have more soon. They’re the Mint, after all. Printing money is pretty much all they do.