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	$45.50	4.290%	$47.452	$47.45	$47.45	$47.50
Purchase #2	$56.39	7.556%	$60.6508	$60.65	$60.65	$60.70
Purchase #3	$71.78	9.291%	$78.4491	$78.45	$78.45	$78.40
Purchase #4	$13.89	3.491%	$14.3749	$14.37	$14.35	$14.40
Purchase #5	$19.98	9.712%	$21.9205	$21.92	$21.90	$21.90
Purchase #6	$72.96	5.756%	$77.1596	$77.16	$77.15	$77.20
Purchase #7	$198.93	9.112%	$217.0565	$217.06	$217.05	$217.10
7 purchase totals =	$479.43		$517.0634	$517.06	$517.00	$517.20