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	$214.75	8.830%	$233.7124	$233.71	$233.70	$233.70
Purchase #2	$50.96	3.643%	$52.8165	$52.82	$52.80	$52.80
Purchase #3	$92.25	13.589%	$104.7859	$104.79	$104.80	$104.80
Purchase #4	$96.94	7.546%	$104.2551	$104.26	$104.25	$104.30
Purchase #5	$241.88	13.166%	$273.7259	$273.73	$273.75	$273.70
Purchase #6	$111.45	4.580%	$116.5544	$116.55	$116.55	$116.60
Purchase #7	$192.60	11.550%	$214.8453	$214.85	$214.85	$214.80
7 purchase totals =	$1,000.83		$1,100.6955	$1,100.71	$1,100.70	$1,100.70