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	$126.83	4.810%	$132.9305	$132.93	$132.95	$132.90
Purchase #2	$87.69	3.278%	$90.5645	$90.56	$90.55	$90.60
Purchase #3	$57.52	5.108%	$60.4581	$60.46	$60.45	$60.50
Purchase #4	$67.71	13.187%	$76.6389	$76.64	$76.65	$76.60
Purchase #5	$132.36	10.793%	$146.6456	$146.65	$146.65	$146.60
Purchase #6	$183.52	7.261%	$196.8454	$196.85	$196.85	$196.80
Purchase #7	$16.95	10.300%	$18.6959	$18.70	$18.70	$18.70
7 purchase totals =	$672.58		$722.7789	$722.79	$722.80	$722.70