"Left- number bias" refers to when people focus on the left-hand number--and thus, why so many prices in stores take the form of $X and 99 cents, rather than rounding up that extra penny.
Avner Strulov-Shlain offers some additional evidence on this well-known phenomenon and then draws out some lesser-known implications in "More than a Penny's Worth: Left-Digit Bias and Firm Pricing" (December 2019, Chicago Booth Research Paper No. 19-22). The Chicago Booth Review offers a short readable overview here.
Strulov-Shlain estimated demand curves for products. However, in the model he uses, raising price by a certain amount (say, by a penny or a dime) are allowed to have a bigger effect when it changes the left-hand dollar value than when it doesn't change the left-hand dollar value. He writes:
Timothy Taylor is an American economist. He is managing editor of the Journal of Economic Perspectives, a quarterly academic journal produced at Macalester College and published by the American Economic Association. Taylor received his Bachelor of Arts degree from Haverford College and a master's degree in economics from Stanford University. At Stanford, he was winner of the award for excellent teaching in a large class (more than 30 students) given by the Associated Students of Stanford University. At Minnesota, he was named a Distinguished Lecturer by the Department of Economics and voted Teacher of the Year by the master's degree students at the Hubert H. Humphrey Institute of Public Affairs. Taylor has been a guest speaker for groups of teachers of high school economics, visiting diplomats from eastern Europe, talk-radio shows, and community groups. From 1989 to 1997, Professor Taylor wrote an economics opinion column for the San Jose Mercury-News. He has published multiple lectures on economics through The Teaching Company. With Rudolph Penner and Isabel Sawhill, he is co-author of Updating America's Social Contract (2000), whose first chapter provided an early radical centrist perspective, "An Agenda for the Radical Middle". Taylor is also the author of The Instant Economist: Everything You Need to Know About How the Economy Works, published by the Penguin Group in 2012. The fourth edition of Taylor's Principles of Economics textbook was published by Textbook Media in 2017.