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	$152.43	8.716%	$165.7158	$165.72	$165.70	$165.70
Purchase #2	$199.46	3.429%	$206.2995	$206.30	$206.30	$206.30
Purchase #3	$117.52	12.694%	$132.438	$132.44	$132.45	$132.40
Purchase #4	$207.96	11.858%	$232.6199	$232.62	$232.60	$232.60
Purchase #5	$148.59	13.544%	$168.715	$168.72	$168.70	$168.70
Purchase #6	$72.45	6.462%	$77.1317	$77.13	$77.15	$77.10
Purchase #7	$71.30	10.227%	$78.5919	$78.59	$78.60	$78.60
7 purchase totals =	$969.71		$1,061.5118	$1,061.52	$1,061.50	$1,061.40