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	$190.79	8.257%	$206.5435	$206.54	$206.55	$206.50
Purchase #2	$88.57	8.102%	$95.7459	$95.75	$95.75	$95.70
Purchase #3	$99.99	11.601%	$111.5898	$111.59	$111.60	$111.60
Purchase #4	$124.52	3.427%	$128.7873	$128.79	$128.80	$128.80
Purchase #5	$111.85	5.138%	$117.5969	$117.60	$117.60	$117.60
Purchase #6	$223.79	10.637%	$247.5945	$247.59	$247.60	$247.60
Purchase #7	$97.48	3.402%	$100.7963	$100.80	$100.80	$100.80
7 purchase totals =	$936.99		$1,008.6542	$1,008.66	$1,008.70	$1,008.60