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	$104.93	13.250%	$118.8332	$118.83	$118.85	$118.80
Purchase #2	$198.39	5.829%	$209.9542	$209.95	$209.95	$210.00
Purchase #3	$34.46	11.361%	$38.375	$38.38	$38.40	$38.40
Purchase #4	$124.83	5.769%	$132.0314	$132.03	$132.05	$132.00
Purchase #5	$55.79	6.238%	$59.2702	$59.27	$59.25	$59.30
Purchase #6	$52.85	8.340%	$57.2577	$57.26	$57.25	$57.30
Purchase #7	$220.78	11.720%	$246.6554	$246.66	$246.65	$246.70
7 purchase totals =	$792.03		$862.3771	$862.38	$862.40	$862.50