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	$221.80	4.597%	$231.9961	$232.00	$232.00	$232.00
Purchase #2	$61.77	11.199%	$68.6876	$68.69	$68.70	$68.70
Purchase #3	$94.82	12.578%	$106.7465	$106.75	$106.75	$106.70
Purchase #4	$54.47	9.446%	$59.6152	$59.62	$59.60	$59.60
Purchase #5	$17.72	4.297%	$18.4814	$18.48	$18.50	$18.50
Purchase #6	$138.85	4.548%	$145.1649	$145.16	$145.15	$145.20
Purchase #7	$107.82	3.398%	$111.4837	$111.48	$111.50	$111.50
7 purchase totals =	$697.25		$742.1754	$742.18	$742.20	$742.20