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	$150.75	13.208%	$170.6611	$170.66	$170.65	$170.70
Purchase #2	$214.52	3.521%	$222.0732	$222.07	$222.05	$222.10
Purchase #3	$239.90	6.337%	$255.1025	$255.10	$255.10	$255.10
Purchase #4	$229.82	11.172%	$255.4955	$255.50	$255.50	$255.50
Purchase #5	$155.68	12.410%	$174.9999	$175.00	$175.00	$175.00
Purchase #6	$103.58	12.166%	$116.1815	$116.18	$116.20	$116.20
Purchase #7	$11.95	13.123%	$13.5182	$13.52	$13.50	$13.50
7 purchase totals =	$1,106.20		$1,208.0319	$1,208.03	$1,208.00	$1,208.10