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	$130.78	9.261%	$142.8915	$142.89	$142.90	$142.90
Purchase #2	$141.47	8.841%	$153.9774	$153.98	$154.00	$154.00
Purchase #3	$229.55	11.480%	$255.9023	$255.90	$255.90	$255.90
Purchase #4	$138.93	9.298%	$151.8477	$151.85	$151.85	$151.80
Purchase #5	$47.97	4.659%	$50.2049	$50.20	$50.20	$50.20
Purchase #6	$60.57	9.410%	$66.2696	$66.27	$66.25	$66.30
Purchase #7	$148.56	5.849%	$157.2493	$157.25	$157.25	$157.20
7 purchase totals =	$897.83		$978.3427	$978.34	$978.35	$978.30