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	$81.62	9.788%	$89.609	$89.61	$89.60	$89.60
Purchase #2	$62.66	6.505%	$66.736	$66.74	$66.75	$66.70
Purchase #3	$243.66	4.158%	$253.7914	$253.79	$253.80	$253.80
Purchase #4	$240.73	7.132%	$257.8989	$257.90	$257.90	$257.90
Purchase #5	$6.54	8.443%	$7.0922	$7.09	$7.10	$7.10
Purchase #6	$53.95	10.726%	$59.7367	$59.74	$59.75	$59.70
Purchase #7	$207.48	5.844%	$219.6051	$219.61	$219.60	$219.60
7 purchase totals =	$896.64		$954.4693	$954.48	$954.50	$954.40