Suppose an airplane is flying from St. Louis to Hawaii... it needs 354 gallons of fuel to reach the west coast and another 291 gallons of fuel to get from the west coast to Hawaii. How many gallons of fuel must the pilot put in his plane to make sure he gets to Hawaii?
300 + 200 = 500... close enough.
If they had rounded correctly to the nearest hundred they still would have run out of fuel but might have been able to glide the last 45 miles.
I have a BS degree in Business Administration and a MBA.
My senior year in college, my landlord and also an accounting professor gave me some great advice re checking accts.
His advice was to forget about the pennies. If the cents were under 33 cents on a check, round down to the nearest $. If over 33 cents round up to the nearest $.
We have used that advice for over 50+ years with our personal checking accts., and we have never had a problem.
A friend, with a Masters in Accting and years as a CFO for big and small companies uses that rounding system with his non profits. He never has a problem.
I have used the rounding up or down in most aspects of my life with no problems. I have never run out of gasoline on a trip or just driving around town. I know when/where to stop to eat on a long road trip.
Many fly fishers with the one or two handed rods carry and/or use a small electronic scale to weigh their lines, leaders and even flies. I use a simple SWAG system, and it works. I know with a couple of practice casts if the fly line and terminal system is too light, too long, too short, too heavy or too light or just right.
However, the rounding up or down could be a disaster if one is in medicine, heavy duty construction, flying an airplane, payroll accounting, and other services where accurate math is a must.