Rounding of tax amounts mandates nearest-unit adjustment so fractional currency at or above a threshold rounds up and lower fractions ignored. Section requires rounding off to the nearest rupee for all payable sums and refunds under the Act: fractional parts of a rupee expressed as paise are increased to the next rupee when they meet or exceed the statutory threshold, and are ignored when below that threshold, ensuring uniform adjustment of tax, interest, penalty, fine and refund amounts.