"nearest pound" means we need to round the number to become a whole number of pounds (either up or down).
14.65 pounds is the cost of bag B.
you would have to subtract 0.65 pounds to get 14 pounds.
Alternatively, you could add 0.35 pounds to get to 15 pounds.
Of these, 0.35 is smaller meaning 14.65 is nearest to 15.
Let me know if this needs further explaining :)