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	$189.59	11.116%	$210.6648	$210.66	$210.65	$210.70
Purchase #2	$38.87	10.623%	$42.9992	$43.00	$43.00	$43.00
Purchase #3	$145.51	5.102%	$152.9339	$152.93	$152.95	$152.90
Purchase #4	$140.39	8.816%	$152.7668	$152.77	$152.75	$152.80
Purchase #5	$247.51	4.205%	$257.9178	$257.92	$257.90	$257.90
Purchase #6	$175.45	8.557%	$190.4633	$190.46	$190.45	$190.50
Purchase #7	$10.35	10.798%	$11.4676	$11.47	$11.45	$11.50
7 purchase totals =	$947.67		$1,019.2134	$1,019.21	$1,019.15	$1,019.30