I round up but not to the level that the first poster does.
If something comes in at 292 calories, I'll round up to 300. Or if it comes in at 67 (like my afternoon apple), I'll round up to 70. It just makes it easier to add in my head.
But I don't round up to the nearest 100 or nearest 50 or whatever. I'd wind up making myself crazy that way! And I am one of those poeple who sets the clock forward 10 minutes and then lies in bed an tries to calculate how many minutes I *really* have to hit the snooze alarm!
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