Can someone explain to me how to round to the nearest 10 dollars?

Pinpoint the ten's place.
look at the one's place. It is a digit ≥5, round up. If it is digit <5, round down.
all the digits to the right of the ten's place becomes 0.
for example, if you are given $216.23, the ten's place is a 1. Look at the number to the right of it, the one's place is a 6, bigger than 5, so you round up, the 1 becomes a 2. the result is $220.00
if you are given $214.23, the 1 stays a 1 because 4 is smaller than 5, the result is $210.00