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	$125.89	6.476%	$134.0426	$134.04	$134.05	$134.00
Purchase #2	$247.45	7.716%	$266.5432	$266.54	$266.55	$266.50
Purchase #3	$199.86	8.389%	$216.6263	$216.63	$216.65	$216.60
Purchase #4	$50.32	12.773%	$56.7474	$56.75	$56.75	$56.70
Purchase #5	$63.88	10.357%	$70.4961	$70.50	$70.50	$70.50
Purchase #6	$61.50	10.208%	$67.7779	$67.78	$67.80	$67.80
Purchase #7	$74.55	10.823%	$82.6185	$82.62	$82.60	$82.60
7 purchase totals =	$823.45		$894.8520	$894.86	$894.90	$894.70