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	$92.58	8.509%	$100.4576	$100.46	$100.45	$100.50
Purchase #2	$76.67	8.339%	$83.0635	$83.06	$83.05	$83.10
Purchase #3	$95.93	4.508%	$100.2545	$100.25	$100.25	$100.30
Purchase #4	$141.88	11.591%	$158.3253	$158.33	$158.35	$158.30
Purchase #5	$27.47	7.123%	$29.4267	$29.43	$29.45	$29.40
Purchase #6	$187.30	6.250%	$199.0063	$199.01	$199.00	$199.00
Purchase #7	$116.92	6.295%	$124.2801	$124.28	$124.30	$124.30
7 purchase totals =	$738.75		$794.8140	$794.82	$794.85	$794.90