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	$80.83	6.172%	$85.8188	$85.82	$85.80	$85.80
Purchase #2	$235.77	8.599%	$256.0439	$256.04	$256.05	$256.00
Purchase #3	$173.36	3.171%	$178.8572	$178.86	$178.85	$178.90
Purchase #4	$160.40	13.643%	$182.2834	$182.28	$182.30	$182.30
Purchase #5	$11.90	8.742%	$12.9403	$12.94	$12.95	$12.90
Purchase #6	$139.37	5.434%	$146.9434	$146.94	$146.95	$146.90
Purchase #7	$205.45	8.391%	$222.6893	$222.69	$222.70	$222.70
7 purchase totals =	$1,007.08		$1,085.5763	$1,085.57	$1,085.60	$1,085.50