The owner of the Java U franchise, Gary Brown, has two tip cups by the cash register, with one featuring a picture of the U.S. senator from Illinois and his rival, Sen. John McCain, R-Ariz., The Gazette newspaper reported.
The cups have been in place for three weeks and Brown said his staff keep an eye on customers' behavior.
"The kids did a calculation the other day, and 94 percent of the tips went into the Obama cup," he said.
At least 10 times customers dumped the tips from the McCain cup into the Obama cup, the report said.
Brown said he tried to find equally representative photos of the two senators but had problems.
"It was hard to find a picture of McCain that made him look sympathetic -- he always looks angry," Brown told The Gazette.