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	$48.68	9.227%	$53.1717	$53.17	$53.15	$53.20
Purchase #2	$126.87	4.514%	$132.5969	$132.60	$132.60	$132.60
Purchase #3	$70.58	3.333%	$72.9324	$72.93	$72.95	$72.90
Purchase #4	$82.86	7.105%	$88.7472	$88.75	$88.75	$88.70
Purchase #5	$238.71	5.437%	$251.6887	$251.69	$251.70	$251.70
Purchase #6	$53.38	11.740%	$59.6468	$59.65	$59.65	$59.60
Purchase #7	$215.57	11.245%	$239.8108	$239.81	$239.80	$239.80
7 purchase totals =	$836.65		$898.5945	$898.60	$898.60	$898.50