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	$58.59	3.142%	$60.4309	$60.43	$60.45	$60.40
Purchase #2	$71.35	7.598%	$76.7712	$76.77	$76.75	$76.80
Purchase #3	$64.48	6.289%	$68.5351	$68.54	$68.55	$68.50
Purchase #4	$194.32	6.498%	$206.9469	$206.95	$206.95	$206.90
Purchase #5	$105.84	5.557%	$111.7215	$111.72	$111.70	$111.70
Purchase #6	$208.61	8.141%	$225.5929	$225.59	$225.60	$225.60
Purchase #7	$51.31	11.109%	$57.01	$57.01	$57.00	$57.00
7 purchase totals =	$754.50		$807.0085	$807.01	$807.00	$806.90