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	$134.86	8.536%	$146.3716	$146.37	$146.35	$146.40
Purchase #2	$112.43	13.256%	$127.3337	$127.33	$127.35	$127.30
Purchase #3	$151.38	11.516%	$168.8129	$168.81	$168.80	$168.80
Purchase #4	$84.45	13.597%	$95.9327	$95.93	$95.95	$95.90
Purchase #5	$233.25	5.767%	$246.7015	$246.70	$246.70	$246.70
Purchase #6	$79.30	5.205%	$83.4276	$83.43	$83.45	$83.40
Purchase #7	$142.97	4.280%	$149.0891	$149.09	$149.10	$149.10
7 purchase totals =	$938.64		$1,017.6691	$1,017.66	$1,017.70	$1,017.60