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	$170.37	4.320%	$177.73	$177.73	$177.75	$177.70
Purchase #2	$19.60	8.754%	$21.3158	$21.32	$21.30	$21.30
Purchase #3	$38.52	4.239%	$40.1529	$40.15	$40.15	$40.20
Purchase #4	$175.84	8.233%	$190.3169	$190.32	$190.30	$190.30
Purchase #5	$117.75	10.491%	$130.1032	$130.10	$130.10	$130.10
Purchase #6	$206.92	7.367%	$222.1638	$222.16	$222.15	$222.20
Purchase #7	$73.89	11.752%	$82.5736	$82.57	$82.55	$82.60
7 purchase totals =	$802.89		$864.3562	$864.35	$864.30	$864.40