Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$137.29	3.798%	$142.5043	$142.50	$142.50	$142.50
Purchase #2	$44.51	13.239%	$50.4027	$50.40	$50.40	$50.40
Purchase #3	$111.85	3.730%	$116.022	$116.02	$116.00	$116.00
Purchase #4	$73.40	12.207%	$82.3599	$82.36	$82.35	$82.40
Purchase #5	$62.88	5.604%	$66.4038	$66.40	$66.40	$66.40
Purchase #6	$108.79	11.278%	$121.0593	$121.06	$121.05	$121.10
Purchase #7	$202.61	9.823%	$222.5124	$222.51	$222.50	$222.50
7 purchase totals =	$741.33		$801.2644	$801.25	$801.20	$801.30