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	$79.98	10.521%	$88.3947	$88.39	$88.40	$88.40
Purchase #2	$71.38	9.804%	$78.3781	$78.38	$78.40	$78.40
Purchase #3	$59.83	11.483%	$66.7003	$66.70	$66.70	$66.70
Purchase #4	$241.78	11.536%	$269.6717	$269.67	$269.65	$269.70
Purchase #5	$187.51	6.491%	$199.6813	$199.68	$199.70	$199.70
Purchase #6	$180.71	5.209%	$190.1232	$190.12	$190.10	$190.10
Purchase #7	$168.39	7.283%	$180.6538	$180.65	$180.65	$180.70
7 purchase totals =	$989.58		$1,073.6031	$1,073.59	$1,073.60	$1,073.70