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	$63.42	6.685%	$67.6596	$67.66	$67.65	$67.70
Purchase #2	$83.47	11.720%	$93.2527	$93.25	$93.25	$93.30
Purchase #3	$9.25	8.593%	$10.0449	$10.04	$10.05	$10.00
Purchase #4	$78.38	6.518%	$83.4888	$83.49	$83.50	$83.50
Purchase #5	$152.38	13.208%	$172.5064	$172.51	$172.50	$172.50
Purchase #6	$162.62	6.865%	$173.7839	$173.78	$173.80	$173.80
Purchase #7	$108.28	3.492%	$112.0611	$112.06	$112.05	$112.10
7 purchase totals =	$657.80		$712.7974	$712.79	$712.80	$712.90