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	$73.38	11.571%	$81.8708	$81.87	$81.85	$81.90
Purchase #2	$18.29	3.395%	$18.9109	$18.91	$18.90	$18.90
Purchase #3	$104.94	6.250%	$111.4988	$111.50	$111.50	$111.50
Purchase #4	$66.34	9.724%	$72.7909	$72.79	$72.80	$72.80
Purchase #5	$61.63	7.160%	$66.0427	$66.04	$66.05	$66.00
Purchase #6	$222.45	3.593%	$230.4426	$230.44	$230.45	$230.40
Purchase #7	$116.75	13.238%	$132.2054	$132.21	$132.20	$132.20
7 purchase totals =	$663.78		$713.7621	$713.76	$713.75	$713.70