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	$99.69	8.341%	$108.0051	$108.01	$108.00	$108.00
Purchase #2	$18.56	5.146%	$19.5151	$19.52	$19.50	$19.50
Purchase #3	$236.26	8.244%	$255.7373	$255.74	$255.75	$255.70
Purchase #4	$12.49	7.874%	$13.4735	$13.47	$13.45	$13.50
Purchase #5	$69.25	4.808%	$72.5795	$72.58	$72.60	$72.60
Purchase #6	$233.57	10.617%	$258.3681	$258.37	$258.35	$258.40
Purchase #7	$62.68	7.286%	$67.2469	$67.25	$67.25	$67.20
7 purchase totals =	$732.50		$794.9255	$794.94	$794.90	$794.90