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	$198.50	12.234%	$222.7845	$222.78	$222.80	$222.80
Purchase #2	$54.70	12.598%	$61.5911	$61.59	$61.60	$61.60
Purchase #3	$52.93	4.445%	$55.2827	$55.28	$55.30	$55.30
Purchase #4	$62.88	5.619%	$66.4132	$66.41	$66.40	$66.40
Purchase #5	$231.37	11.195%	$257.2719	$257.27	$257.25	$257.30
Purchase #6	$21.42	13.504%	$24.3126	$24.31	$24.30	$24.30
Purchase #7	$32.51	4.735%	$34.0493	$34.05	$34.05	$34.00
7 purchase totals =	$654.31		$721.7053	$721.69	$721.70	$721.70