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	$53.96	10.810%	$59.7931	$59.79	$59.80	$59.80
Purchase #2	$48.42	6.129%	$51.3877	$51.39	$51.40	$51.40
Purchase #3	$58.31	13.829%	$66.3737	$66.37	$66.35	$66.40
Purchase #4	$111.66	5.384%	$117.6718	$117.67	$117.65	$117.70
Purchase #5	$92.79	6.103%	$98.453	$98.45	$98.45	$98.50
Purchase #6	$181.89	11.654%	$203.0875	$203.09	$203.10	$203.10
Purchase #7	$52.43	8.230%	$56.745	$56.75	$56.75	$56.70
7 purchase totals =	$599.46		$653.5118	$653.51	$653.50	$653.60