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	$220.89	7.195%	$236.783	$236.78	$236.80	$236.80
Purchase #2	$192.62	13.109%	$217.8706	$217.87	$217.85	$217.90
Purchase #3	$128.26	11.868%	$143.4819	$143.48	$143.50	$143.50
Purchase #4	$97.53	4.782%	$102.1939	$102.19	$102.20	$102.20
Purchase #5	$32.77	6.493%	$34.8978	$34.90	$34.90	$34.90
Purchase #6	$111.71	4.385%	$116.6085	$116.61	$116.60	$116.60
Purchase #7	$156.28	5.622%	$165.0661	$165.07	$165.05	$165.10
7 purchase totals =	$940.06		$1,016.9018	$1,016.90	$1,016.90	$1,017.00