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	$43.47	4.603%	$45.4709	$45.47	$45.45	$45.50
Purchase #2	$58.60	13.223%	$66.3487	$66.35	$66.35	$66.30
Purchase #3	$172.30	12.554%	$193.9305	$193.93	$193.95	$193.90
Purchase #4	$99.80	6.145%	$105.9327	$105.93	$105.95	$105.90
Purchase #5	$199.97	7.529%	$215.0257	$215.03	$215.05	$215.00
Purchase #6	$9.36	13.257%	$10.6009	$10.60	$10.60	$10.60
Purchase #7	$95.93	9.608%	$105.147	$105.15	$105.15	$105.10
7 purchase totals =	$679.43		$742.4564	$742.46	$742.50	$742.30