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	$204.27	9.449%	$223.5715	$223.57	$223.55	$223.60
Purchase #2	$147.68	9.422%	$161.5944	$161.59	$161.60	$161.60
Purchase #3	$181.31	5.239%	$190.8088	$190.81	$190.80	$190.80
Purchase #4	$65.53	10.575%	$72.4598	$72.46	$72.45	$72.50
Purchase #5	$74.34	4.738%	$77.8622	$77.86	$77.85	$77.90
Purchase #6	$102.67	8.815%	$111.7204	$111.72	$111.70	$111.70
Purchase #7	$37.26	11.323%	$41.4789	$41.48	$41.50	$41.50
7 purchase totals =	$813.06		$879.4960	$879.49	$879.45	$879.60