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	$108.26	10.587%	$119.7215	$119.72	$119.70	$119.70
Purchase #2	$95.68	4.201%	$99.6995	$99.70	$99.70	$99.70
Purchase #3	$47.76	9.307%	$52.205	$52.21	$52.20	$52.20
Purchase #4	$202.89	13.319%	$229.9129	$229.91	$229.90	$229.90
Purchase #5	$54.75	5.697%	$57.8691	$57.87	$57.85	$57.90
Purchase #6	$116.26	3.621%	$120.4698	$120.47	$120.45	$120.50
Purchase #7	$177.44	10.712%	$196.4474	$196.45	$196.45	$196.40
7 purchase totals =	$803.04		$876.3252	$876.33	$876.25	$876.30