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	$65.75	8.519%	$71.3512	$71.35	$71.35	$71.40
Purchase #2	$20.56	11.168%	$22.8561	$22.86	$22.85	$22.90
Purchase #3	$59.55	11.629%	$66.4751	$66.48	$66.50	$66.50
Purchase #4	$142.37	8.602%	$154.6167	$154.62	$154.60	$154.60
Purchase #5	$131.70	10.671%	$145.7537	$145.75	$145.75	$145.80
Purchase #6	$176.95	11.189%	$196.7489	$196.75	$196.75	$196.70
Purchase #7	$172.58	3.139%	$177.9973	$178.00	$178.00	$178.00
7 purchase totals =	$769.46		$835.7990	$835.81	$835.80	$835.90