You need to be organized.
Put the $1's in a waste basket till you cannot squash another one in.
Then trade them in for $5's or $10's an stack them neatly in an old shoe box.
When you have 10 or more boxes of $5's and $10's trade them in for $100's.
With 20 or more shoe boxes full of $100's it's time to trade them in for some gold bricks. We like to keep a few dozen of those around just in case.
Semper Fi