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	$163.34	10.591%	$180.6393	$180.64	$180.65	$180.60
Purchase #2	$228.63	11.430%	$254.7624	$254.76	$254.75	$254.80
Purchase #3	$214.99	6.671%	$229.332	$229.33	$229.35	$229.30
Purchase #4	$39.45	3.720%	$40.9175	$40.92	$40.90	$40.90
Purchase #5	$171.47	4.654%	$179.4502	$179.45	$179.45	$179.50
Purchase #6	$250.64	5.542%	$264.5305	$264.53	$264.55	$264.50
Purchase #7	$111.79	4.560%	$116.8876	$116.89	$116.90	$116.90
7 purchase totals =	$1,180.31		$1,266.5195	$1,266.52	$1,266.55	$1,266.50