so 10.38 gal at 2.289 oer gal but you want american mony so round 2.289 to two decimal places so 2.29 per gallon
2.29 times 10.38=23.7702 but you just cross out the '2' in the ten-thousanth's place because 1/50 of a cent is really small
it is not possible to pay 9/10 of a cent so they just want you to round it up to 1 cent or10/10 cent