When you record your bank deposits of course it is very important if you have received cheques to match these correctly to the actual bank deposit. When you receive mostly cash it is not easy to match what you deposit to what you have received. Often you will have taken some of the cash and used it for petty cash items, so it never actually makes it to the bank.
Some businesses still want to exactly account for their cash. This is often quite a good idea. When they do this they make it a practice to never use money from the till to make purchases, rather they have a separate petty cash tin for this. Any money taken from the till to put into the petty cash tin is properly recorded as a transfer from Undeposited funds to the Petty cash account.
Businesses using this method can straight away track to the dollar any missing money and will know straight away if anyone (i.e; employees) have their hand in the till or if any sales or purchases are not being properly recorded. Any business that has employees would be silly not to use this method. If employees know that this sort of tracking is being done then it removes all temptation before it even happens.