Marketplace Pick: Your Bill Whiz
Your Bill Whiz is a finder friendly application that will help calculate your bills while having the option to split it among friends. The program has a built in calculator to estimate the total cost in case you are on a budget and want to know what the total cost will be before you order. There are even options to calculate both tax and gratuity based on your regions sales tax and what you would want to pay as gratuity. Your Bill Whiz costs $0.99 on Windows Mobile Marketplace but free if you want to try the basic version of Your Bill.