Many shops have prices set just under a round figure, e.g. $9.99 instead of $10.00 or $99.95 instead of $100.00 . It is assumed that this is done because the price seems lower to the consumer. But this is not the reason the practice started. What was the original reason for this pricing method?

The practice originated to ensure that the clerk had to open the till and give change for each transaction, thus recording the sale and preventing him from pocketing the bank notes.