The nation’s largest retail chain is experimenting with same-day deliveries for its online sales.

Wal-Mart (NYSE:WMT) is rolling out such an option in five markets across the country for the holidays. Customers who want the items they purchase at Wal-Mart’s online store delivered the same day will pay an additional $10, The New York Times notes.

Online shoppers can then expect their products delivered during a four-hour window. The retailer is also offering next-day delivery for the same price.

While Wal-Mart didn’t disclose the exact numbers of online customers requesting same-day deliveries, a spokesperson noted that many customers selected the next-day option instead.

A number of companies are testing same-day shipping options, including eBay (NASDAQ:EBAY), though the cost and logistics problems remain daunting. Analysts said that the driving motivation to offer same-day shipping was a need to compete with Amazon (NASDAQ:AMZN).

While Wal-Mart’s online sales are tiny compared to Amazon’s, the company noted that same-day delivery boosted customer convenience. The U.S. Postal Service also tested a limited same-day delivery option for certain retailers this holiday season.

Shares of Wal-Mart slipped fractionally in Friday morning trading.