To prevent unfinalized sales, at the end of your shift hit the Auto Recall button. This will load any unfinalized sales in a list for you to choose to open. You may then finalize the sale. Repeat for each unfinalized sale.
If the auto-recall button does not recall the sale, and you know you have an unfinalized sale, press the following:
You will then see the following screen where you can search for an unfinalized sale.