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	$154.59	9.238%	$168.871	$168.87	$168.85	$168.90
Purchase #2	$35.90	12.421%	$40.3591	$40.36	$40.35	$40.40
Purchase #3	$30.78	13.545%	$34.9492	$34.95	$34.95	$34.90
Purchase #4	$158.70	9.162%	$173.2401	$173.24	$173.25	$173.20
Purchase #5	$77.86	10.294%	$85.8749	$85.87	$85.85	$85.90
Purchase #6	$52.90	13.130%	$59.8458	$59.85	$59.85	$59.80
Purchase #7	$57.28	11.614%	$63.9325	$63.93	$63.95	$63.90
7 purchase totals =	$568.01		$627.0726	$627.07	$627.05	$627.00