Why do prices end in .99?

People may ask a very common question: "How come prices end in .99 when you buy a lot of things at the supermarket. Why the retailers set the prices like that? How is its effect to the buyers?

The answer is: "This is the psychological pricing strategy in business", This strategy is focused on the ego and self image of buyers. For example, when people buy something, they look at the price of  2.99$ and feel they are getting the "deal", this price is sounds much cheaper than 3$ because in their imagination is just "2". This strategy doesn't work for everyone but actually it's very helpful in supporting the selling strategies.

However, some suggest that intentionally awkward pricing was adopted primarily to control employee theft, before the turn of the 20th century when stores expanded beyond owner-operators and used cash registers. For cash transactions with an odd price, most customers must be given change. Creating change requires the employee to open the cash register, recording the sale. This reduces the risk of the cashier stealing from the store owner?