So here is my theory: Download the TipKalc for your iPod and even though it costs $4.99 you'll end up saving money.
If you don't have a fancy schmancy cell phone with a tip calculator the TipKalc widget for your iPod might be the answer to all your dinner-table scribbling woes. You just spin your iPod click wheel until you get to your bill amount and everything is calculated for you.