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	$153.69	7.533%	$165.2675	$165.27	$165.25	$165.30
Purchase #2	$217.92	11.397%	$242.7563	$242.76	$242.75	$242.80
Purchase #3	$205.43	11.863%	$229.8002	$229.80	$229.80	$229.80
Purchase #4	$106.56	4.607%	$111.4692	$111.47	$111.45	$111.50
Purchase #5	$9.51	11.862%	$10.6381	$10.64	$10.65	$10.60
Purchase #6	$12.70	10.136%	$13.9873	$13.99	$14.00	$14.00
Purchase #7	$100.64	11.230%	$111.9419	$111.94	$111.95	$111.90
7 purchase totals =	$806.45		$885.8605	$885.87	$885.85	$885.90