It’s certainly a laudable act to seek to return $762 dollars found on the ground by an ATM. Few, indeed, would fault a man for predicting the rightful owner to be unlocatable and pocketing the money. Even fewer, I’d say, would find it blameworthy to keep the money if the authorities wouldn’t hand over even a portion should the owner not be tracked down, as Anthony Saccoccia discovered to be the case in Warwick:

He tried to return the money to the Greenwood Credit Union, on Post Road, which was closed. Then he checked a neighboring business, also closed.
So he took the money home and called the police. “We picked it up, brought it in and tagged it as evidence,” said police Lt. Thomas Hannon.
The police will follow up with the credit union to try to figure out how the money got there, and to whom it belongs. They will seek to examine surveillance video and will ask the credit union to review withdrawal records, Hannon said.
Under the law, the money will go into an interest-earning account for six months, he said. If the police cannot locate the rightful owner in that time, the cash will be transferred to the general fund that pays for city services, he said.

Odd that the person to whom the money actually belonged would likely be more generous toward Mr. Saccoccia than the municipal government. Who’d have thought that the honesty tax would be 100%?
ADDENDUM:
According to Jon of Rhode Island Law Journal, Mr. Saccoccia has a right to that money if it’s not claimed. His 90-day clock to claim the money begins when the owner’s 90 days are up.
You may all proceed with your good-samaritanism.