How to pay tithing with multiple strings of income

Paying tithing used to be easy for me when I had one source of income. I just looked at the pay stub, and wrote a check for 10% of my income. Like many people, my wife and I earn money from several places: my wife’s job, online surveys, investments, ect. (Don’t get the impression that we’re rolling in the dough. The money we make from all this stuff is pretty much pennies. But every little bit helps!) How does one keep track of all this?

Over at the Darnit Blog, there’s a great post that attempts to solve such a conundrum. He presents several scenarios that might occur for a family earning money from multiple strings of income. He then shows some possible solutions to keeping track of your tithing in these different situations.