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	$132.27	12.554%	$148.8752	$148.88	$148.90	$148.90
Purchase #2	$9.91	7.498%	$10.6531	$10.65	$10.65	$10.70
Purchase #3	$244.53	4.493%	$255.5167	$255.52	$255.50	$255.50
Purchase #4	$170.72	10.294%	$188.2939	$188.29	$188.30	$188.30
Purchase #5	$61.93	7.756%	$66.7333	$66.73	$66.75	$66.70
Purchase #6	$56.32	11.588%	$62.8464	$62.85	$62.85	$62.80
Purchase #7	$98.25	7.468%	$105.5873	$105.59	$105.60	$105.60
7 purchase totals =	$773.93		$838.5059	$838.51	$838.55	$838.50