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	$179.59	9.616%	$196.8594	$196.86	$196.85	$196.90
Purchase #2	$66.49	6.786%	$71.002	$71.00	$71.00	$71.00
Purchase #3	$51.99	8.180%	$56.2428	$56.24	$56.25	$56.20
Purchase #4	$165.41	4.855%	$173.4407	$173.44	$173.45	$173.40
Purchase #5	$205.79	12.575%	$231.6681	$231.67	$231.65	$231.70
Purchase #6	$152.81	11.433%	$170.2808	$170.28	$170.30	$170.30
Purchase #7	$157.35	10.323%	$173.5932	$173.59	$173.60	$173.60
7 purchase totals =	$979.43		$1,073.0870	$1,073.08	$1,073.10	$1,073.10