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	$37.75	10.234%	$41.6133	$41.61	$41.60	$41.60
Purchase #2	$189.59	4.672%	$198.4476	$198.45	$198.45	$198.40
Purchase #3	$132.55	5.103%	$139.314	$139.31	$139.30	$139.30
Purchase #4	$221.65	5.796%	$234.4968	$234.50	$234.50	$234.50
Purchase #5	$24.94	11.845%	$27.8941	$27.89	$27.90	$27.90
Purchase #6	$184.75	3.787%	$191.7465	$191.75	$191.75	$191.70
Purchase #7	$19.62	13.860%	$22.3393	$22.34	$22.35	$22.30
7 purchase totals =	$810.85		$855.8516	$855.85	$855.85	$855.70