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	$55.82	5.854%	$59.0877	$59.09	$59.10	$59.10
Purchase #2	$72.71	13.496%	$82.5229	$82.52	$82.50	$82.50
Purchase #3	$32.90	4.508%	$34.3831	$34.38	$34.40	$34.40
Purchase #4	$52.62	11.337%	$58.5855	$58.59	$58.60	$58.60
Purchase #5	$169.63	8.548%	$184.13	$184.13	$184.15	$184.10
Purchase #6	$105.48	11.748%	$117.8718	$117.87	$117.85	$117.90
Purchase #7	$170.67	11.208%	$189.7987	$189.80	$189.80	$189.80
7 purchase totals =	$659.83		$726.3797	$726.38	$726.40	$726.40