If the question is "what is $1.8984375 rounded to the nearest dollar?" then:
We're rounding to the ones place. There's a 1 in the ones place. The next digit to the right (8) is greater than or equal to 5, so the 1 rounds up.
Answer: $2
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If we wanted to be super-exact about it, 1.8984375 rounded to the nearest dollar is $0 because 1.8984375 is not a measure of money. Your teacher is probably looking for the $2 version above though.