Yale University
Solving Problems by the Hundreds
This site contains a study of percentage and its applications in the study of consumer related problems. Problems involving sales tax are included. Examples, explanation, solutions and a bibliography are also included in the site.
AAA Math
Aaa Math: Consumer Math
From basics such as adding and subtracting money, converting coins, and making change to more advanced topics such as sales tax and simple interest, this interactive tutorial offers help with consumer math issues.