To round to the nearest pound, we consider the first number after the decimal point; if the number is less that 5, we neglect (throw away) the decimal part but if the number is upto 5, we add 1 to the number before the decimal point.
So, consider 17.55, the number after the decimal point is upto 5, so we add 1 to 17 to get 18.
Therefore, £17.55 rounded to nearest pound is £18.
