To round $273 to the nearest ten, we look at the ones digit, which is 3 in this case. To round a number to the nearest ten, we:
1. Round down (to the lower ten) if the ones digit is less than 5.
2. Round up (to the higher ten) if the ones digit is 5 or more.
Since the ones digit of $273 is 3, which is less than 5, we round down to the lower ten. The tens digit in $273 is 7, so the nearest lower ten is $270.
Therefore, Mario has saved approximately $270 when rounding to the nearest ten.
