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	$93.77	6.129%	$99.5172	$99.52	$99.50	$99.50
Purchase #2	$159.57	5.195%	$167.8597	$167.86	$167.85	$167.90
Purchase #3	$116.68	13.525%	$132.461	$132.46	$132.45	$132.50
Purchase #4	$111.81	5.278%	$117.7113	$117.71	$117.70	$117.70
Purchase #5	$136.65	13.436%	$155.0103	$155.01	$155.00	$155.00
Purchase #6	$243.28	3.821%	$252.5757	$252.58	$252.60	$252.60
Purchase #7	$148.88	12.871%	$168.0423	$168.04	$168.05	$168.00
7 purchase totals =	$1,010.64		$1,093.1775	$1,093.18	$1,093.15	$1,093.20