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	$68.93	9.615%	$75.5576	$75.56	$75.55	$75.60
Purchase #2	$90.42	10.178%	$99.6229	$99.62	$99.60	$99.60
Purchase #3	$100.27	11.584%	$111.8853	$111.89	$111.90	$111.90
Purchase #4	$138.60	7.149%	$148.5085	$148.51	$148.50	$148.50
Purchase #5	$208.52	8.356%	$225.9439	$225.94	$225.95	$225.90
Purchase #6	$137.42	3.720%	$142.532	$142.53	$142.55	$142.50
Purchase #7	$185.43	10.700%	$205.271	$205.27	$205.25	$205.30
7 purchase totals =	$929.59		$1,009.3212	$1,009.32	$1,009.30	$1,009.30