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	$220.52	4.502%	$230.4478	$230.45	$230.45	$230.40
Purchase #2	$100.93	11.430%	$112.4663	$112.47	$112.45	$112.50
Purchase #3	$128.98	11.602%	$143.9443	$143.94	$143.95	$143.90
Purchase #4	$56.42	9.387%	$61.7161	$61.72	$61.70	$61.70
Purchase #5	$69.66	4.432%	$72.7473	$72.75	$72.75	$72.70
Purchase #6	$199.74	10.150%	$220.0136	$220.01	$220.00	$220.00
Purchase #7	$162.57	9.375%	$177.8109	$177.81	$177.80	$177.80
7 purchase totals =	$938.82		$1,019.1463	$1,019.15	$1,019.10	$1,019.00