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	$149.52	11.541%	$166.7761	$166.78	$166.80	$166.80
Purchase #2	$10.81	7.281%	$11.5971	$11.60	$11.60	$11.60
Purchase #3	$145.83	11.195%	$162.1557	$162.16	$162.15	$162.20
Purchase #4	$61.82	9.370%	$67.6125	$67.61	$67.60	$67.60
Purchase #5	$190.33	8.144%	$205.8305	$205.83	$205.85	$205.80
Purchase #6	$68.99	6.496%	$73.4716	$73.47	$73.45	$73.50
Purchase #7	$129.28	7.667%	$139.1919	$139.19	$139.20	$139.20
7 purchase totals =	$756.58		$826.6354	$826.64	$826.65	$826.70