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	$99.60	13.303%	$112.8498	$112.85	$112.85	$112.80
Purchase #2	$157.65	12.152%	$176.8076	$176.81	$176.80	$176.80
Purchase #3	$72.85	11.637%	$81.3276	$81.33	$81.35	$81.30
Purchase #4	$183.25	12.268%	$205.7311	$205.73	$205.75	$205.70
Purchase #5	$235.87	8.627%	$256.2185	$256.22	$256.20	$256.20
Purchase #6	$107.89	8.600%	$117.1685	$117.17	$117.15	$117.20
Purchase #7	$62.46	6.560%	$66.5574	$66.56	$66.55	$66.60
7 purchase totals =	$919.57		$1,016.6605	$1,016.67	$1,016.65	$1,016.60