The phrase "last penny" means the very last bit of money someone has. It refers to the amount of money remaining after all other expenses have been paid and represents having no more funds left. Full definition
The first step to becoming debt free is knowing exactly how much you owe — not what you think you owe, but how much you owe down to the very last penny. (selflender.com)
If they start trying to extract every single last penny then it will be a sad day for gamers. (rdr2.com)
I tell you, nyou will never get out until you have paid the very last penny. (redeeminggod.com)