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	$136.88	3.458%	$141.6133	$141.61	$141.60	$141.60
Purchase #2	$106.88	6.159%	$113.4627	$113.46	$113.45	$113.50
Purchase #3	$52.91	5.581%	$55.8629	$55.86	$55.85	$55.90
Purchase #4	$158.79	4.239%	$165.5211	$165.52	$165.50	$165.50
Purchase #5	$242.75	4.382%	$253.3873	$253.39	$253.40	$253.40
Purchase #6	$227.87	8.536%	$247.321	$247.32	$247.30	$247.30
Purchase #7	$67.90	10.291%	$74.8876	$74.89	$74.90	$74.90
7 purchase totals =	$993.98		$1,052.0559	$1,052.05	$1,052.00	$1,052.10