Numbers affect your mind. People often like working with whole numbers, but when it comes to pricing, items often end in the number 9. And there’s a reason for that.
If you are looking for a bargain, for some reason a dollar to your brain is way more than 99 cents—it's something marketers discovered a long time ago and it's called the left digit effect.
Tim Harford, "Undercover Economist" for the Financial Times, explains the psychology of pricing.