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	$10.36	10.462%	$11.4439	$11.44	$11.45	$11.40
Purchase #2	$56.55	5.449%	$59.6314	$59.63	$59.65	$59.60
Purchase #3	$226.62	5.391%	$238.8371	$238.84	$238.85	$238.80
Purchase #4	$17.74	4.456%	$18.5305	$18.53	$18.55	$18.50
Purchase #5	$194.83	12.178%	$218.5564	$218.56	$218.55	$218.60
Purchase #6	$111.83	9.831%	$122.824	$122.82	$122.80	$122.80
Purchase #7	$13.44	3.439%	$13.9022	$13.90	$13.90	$13.90
7 purchase totals =	$631.37		$683.7255	$683.72	$683.75	$683.60