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	$154.57	7.326%	$165.8938	$165.89	$165.90	$165.90
Purchase #2	$134.76	5.823%	$142.6071	$142.61	$142.60	$142.60
Purchase #3	$161.97	11.526%	$180.6387	$180.64	$180.65	$180.60
Purchase #4	$87.90	8.650%	$95.5034	$95.50	$95.50	$95.50
Purchase #5	$200.83	13.754%	$228.4522	$228.45	$228.45	$228.50
Purchase #6	$117.87	7.565%	$126.7869	$126.79	$126.80	$126.80
Purchase #7	$27.50	4.173%	$28.6476	$28.65	$28.65	$28.60
7 purchase totals =	$885.40		$968.5297	$968.53	$968.55	$968.50