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	$116.75	8.321%	$126.4648	$126.46	$126.45	$126.50
Purchase #2	$100.37	3.384%	$103.7665	$103.77	$103.75	$103.80
Purchase #3	$48.94	10.401%	$54.0302	$54.03	$54.05	$54.00
Purchase #4	$121.35	7.823%	$130.8432	$130.84	$130.85	$130.80
Purchase #5	$161.99	6.538%	$172.5809	$172.58	$172.60	$172.60
Purchase #6	$31.52	10.850%	$34.9399	$34.94	$34.95	$34.90
Purchase #7	$52.32	3.751%	$54.2825	$54.28	$54.30	$54.30
7 purchase totals =	$633.24		$676.9080	$676.90	$676.95	$676.90