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	$229.63	5.546%	$242.3653	$242.37	$242.35	$242.40
Purchase #2	$55.78	7.476%	$59.9501	$59.95	$59.95	$60.00
Purchase #3	$9.66	8.509%	$10.482	$10.48	$10.50	$10.50
Purchase #4	$204.77	9.178%	$223.5638	$223.56	$223.55	$223.60
Purchase #5	$94.85	8.165%	$102.5945	$102.59	$102.60	$102.60
Purchase #6	$196.87	9.468%	$215.5097	$215.51	$215.50	$215.50
Purchase #7	$10.46	11.461%	$11.6588	$11.66	$11.65	$11.70
7 purchase totals =	$802.02		$866.1242	$866.12	$866.10	$866.30