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	$228.52	11.835%	$255.5653	$255.57	$255.55	$255.60
Purchase #2	$112.84	3.674%	$116.9857	$116.99	$117.00	$117.00
Purchase #3	$221.41	3.682%	$229.5623	$229.56	$229.55	$229.60
Purchase #4	$42.32	10.727%	$46.8597	$46.86	$46.85	$46.90
Purchase #5	$122.48	13.609%	$139.1483	$139.15	$139.15	$139.10
Purchase #6	$185.51	13.664%	$210.8581	$210.86	$210.85	$210.90
Purchase #7	$56.82	6.730%	$60.644	$60.64	$60.65	$60.60
7 purchase totals =	$969.90		$1,059.6234	$1,059.63	$1,059.60	$1,059.70