i have found 3 so far. there's also one in the box store but hitting it doesn't do anything. it has been confirmed that there are 4 boxes to find.

There is one in the pub but those are the only four, pub, washroom, beside the super market, and at the vault. I'd suggest hitting them in that order to have the most room for error, but once the vault opens it won't close on a timer.

but it can also easily access it via the vents behind the ATM, but only once the vault has been opened, meaning if the path isn't blocked someone is probably sneaking around in the vault