What is 4.57125 rounded to?

That depends.

-- If you're rounding to the nearest ten-thousandth, it's  4.5713  .
-- If you're rounding to the nearest thousandth, it's  4.571 .
-- If you're rounding to the nearest hundredth, it's  4.57 .
-- If you're rounding to the nearest tenth, it's  4.6 .
-- If you're rounding to the nearest whole number, it's  5 .
-- If you're rounding to the nearest ten, or to any larger place, it's zero.

She will need 5/8 bags for each square yard.