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	$48.32	13.184%	$54.6905	$54.69	$54.70	$54.70
Purchase #2	$128.53	3.569%	$133.1172	$133.12	$133.10	$133.10
Purchase #3	$13.85	11.514%	$15.4447	$15.44	$15.45	$15.40
Purchase #4	$86.28	4.631%	$90.2756	$90.28	$90.30	$90.30
Purchase #5	$18.30	5.391%	$19.2866	$19.29	$19.30	$19.30
Purchase #6	$59.79	10.834%	$66.2676	$66.27	$66.25	$66.30
Purchase #7	$140.39	12.845%	$158.4231	$158.42	$158.40	$158.40
7 purchase totals =	$495.46		$537.5053	$537.51	$537.50	$537.50