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	$43.25	5.428%	$45.5976	$45.60	$45.60	$45.60
Purchase #2	$111.61	10.654%	$123.5009	$123.50	$123.50	$123.50
Purchase #3	$239.56	6.858%	$255.989	$255.99	$256.00	$256.00
Purchase #4	$227.99	7.139%	$244.2662	$244.27	$244.25	$244.30
Purchase #5	$153.68	3.579%	$159.1802	$159.18	$159.20	$159.20
Purchase #6	$84.62	12.560%	$95.2483	$95.25	$95.25	$95.20
Purchase #7	$38.87	11.322%	$43.2709	$43.27	$43.25	$43.30
7 purchase totals =	$899.58		$967.0531	$967.06	$967.05	$967.10