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	$111.57	5.501%	$117.7075	$117.71	$117.70	$117.70
Purchase #2	$156.87	9.841%	$172.3076	$172.31	$172.30	$172.30
Purchase #3	$203.54	6.766%	$217.3115	$217.31	$217.30	$217.30
Purchase #4	$148.71	4.126%	$154.8458	$154.85	$154.85	$154.80
Purchase #5	$224.45	4.388%	$234.2989	$234.30	$234.30	$234.30
Purchase #6	$45.73	13.561%	$51.9314	$51.93	$51.95	$51.90
Purchase #7	$245.72	10.316%	$271.0685	$271.07	$271.05	$271.10
7 purchase totals =	$1,136.59		$1,219.4712	$1,219.48	$1,219.45	$1,219.40