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	$57.76	8.477%	$62.6563	$62.66	$62.65	$62.70
Purchase #2	$95.68	4.641%	$100.1205	$100.12	$100.10	$100.10
Purchase #3	$129.87	12.680%	$146.3375	$146.34	$146.35	$146.30
Purchase #4	$12.40	11.802%	$13.8634	$13.86	$13.85	$13.90
Purchase #5	$48.83	7.401%	$52.4439	$52.44	$52.45	$52.40
Purchase #6	$66.60	9.399%	$72.8597	$72.86	$72.85	$72.90
Purchase #7	$193.49	12.265%	$217.2215	$217.22	$217.20	$217.20
7 purchase totals =	$604.63		$665.5028	$665.50	$665.45	$665.50