The sign for "change" as in "coins" uses an "F" handshape's circled index finger and thumb to represent a couple of coins on the palm of the non-dominant hand.
Place an "F" hand on your palm, then make a little arc up, forward, and down again.
Memory Tip: Think of showing two quarters on the palm of your hand.
COINS / "change"
Here I'm showing three coins (for the camera) but in everyday conversation most signs use no more than two movements thus in high speed sentences you'll see this sign done with "two coins" on the palm.
Note: You could use the COINS sign for "I have some change." (As in, "I have some coins.")
However if you wanted to ask "Do you have change for $5?" -- to be very clear you would sign something along the lines of:
I HAVE FIVE-dollar RECTANGLE, YOU HAVE SWAP? I NEED THREE 1-dollar RECTANGLES PLUS EIGHT 25-cents.
See: EXCHANGE/"swap"
Also see: COIN
Notes: