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	$249.87	6.830%	$266.9361	$266.94	$266.95	$266.90
Purchase #2	$193.80	8.613%	$210.492	$210.49	$210.50	$210.50
Purchase #3	$102.98	8.382%	$111.6118	$111.61	$111.60	$111.60
Purchase #4	$139.25	11.186%	$154.8265	$154.83	$154.85	$154.80
Purchase #5	$57.50	3.749%	$59.6557	$59.66	$59.65	$59.70
Purchase #6	$76.48	3.588%	$79.2241	$79.22	$79.20	$79.20
Purchase #7	$196.75	4.198%	$205.0096	$205.01	$205.00	$205.00
7 purchase totals =	$1,016.63		$1,087.7558	$1,087.76	$1,087.75	$1,087.70