Coins are editable, no checksum whatsoever.
Edit: Alright I figured it out. Dump your save, open it in HXD and change the address 0x00000458 - 0x0000045A to "FF". Like so:
SCORE!
Edit: Alright I figured it out. Dump your save, open it in HXD and change the address 0x00000458 - 0x0000045A to "FF". Like so:
View attachment 132685
You will now have maximum (?) coins.