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	$126.88	4.302%	$132.3384	$132.34	$132.35	$132.30
Purchase #2	$146.54	6.541%	$156.1252	$156.13	$156.15	$156.10
Purchase #3	$77.98	9.344%	$85.2665	$85.27	$85.25	$85.30
Purchase #4	$206.95	7.137%	$221.72	$221.72	$221.70	$221.70
Purchase #5	$85.67	5.588%	$90.4572	$90.46	$90.45	$90.50
Purchase #6	$31.30	11.292%	$34.8344	$34.83	$34.85	$34.80
Purchase #7	$214.57	11.249%	$238.707	$238.71	$238.70	$238.70
7 purchase totals =	$889.89		$959.4487	$959.46	$959.45	$959.40