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	$228.56	6.186%	$242.6987	$242.70	$242.70	$242.70
Purchase #2	$226.27	13.227%	$256.1987	$256.20	$256.20	$256.20
Purchase #3	$67.45	13.418%	$76.5004	$76.50	$76.50	$76.50
Purchase #4	$234.30	4.425%	$244.6678	$244.67	$244.65	$244.70
Purchase #5	$107.89	3.359%	$111.514	$111.51	$111.50	$111.50
Purchase #6	$134.36	10.613%	$148.6196	$148.62	$148.60	$148.60
Purchase #7	$146.37	3.430%	$151.3905	$151.39	$151.40	$151.40
7 purchase totals =	$1,145.20		$1,231.5897	$1,231.59	$1,231.55	$1,231.60