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	$194.25	13.181%	$219.8541	$219.85	$219.85	$219.90
Purchase #2	$89.32	3.468%	$92.4176	$92.42	$92.40	$92.40
Purchase #3	$85.62	6.685%	$91.3437	$91.34	$91.35	$91.30
Purchase #4	$105.81	5.683%	$111.8232	$111.82	$111.80	$111.80
Purchase #5	$58.40	3.160%	$60.2454	$60.25	$60.25	$60.20
Purchase #6	$190.28	9.312%	$207.9989	$208.00	$208.00	$208.00
Purchase #7	$185.47	3.429%	$191.8298	$191.83	$191.85	$191.80
7 purchase totals =	$909.15		$975.5127	$975.51	$975.50	$975.40