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	$182.72	9.768%	$200.5681	$200.57	$200.55	$200.60
Purchase #2	$166.65	5.456%	$175.7424	$175.74	$175.75	$175.70
Purchase #3	$152.26	4.547%	$159.1833	$159.18	$159.20	$159.20
Purchase #4	$34.86	12.705%	$39.289	$39.29	$39.30	$39.30
Purchase #5	$84.57	3.201%	$87.2771	$87.28	$87.30	$87.30
Purchase #6	$100.88	10.837%	$111.8124	$111.81	$111.80	$111.80
Purchase #7	$241.66	11.536%	$269.5379	$269.54	$269.55	$269.50
7 purchase totals =	$963.60		$1,043.4102	$1,043.41	$1,043.45	$1,043.40