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	$89.83	5.328%	$94.6161	$94.62	$94.60	$94.60
Purchase #2	$238.45	8.217%	$258.0434	$258.04	$258.05	$258.00
Purchase #3	$88.89	7.537%	$95.5896	$95.59	$95.60	$95.60
Purchase #4	$230.91	8.474%	$250.4773	$250.48	$250.50	$250.50
Purchase #5	$18.28	9.103%	$19.944	$19.94	$19.95	$19.90
Purchase #6	$62.32	13.285%	$70.5992	$70.60	$70.60	$70.60
Purchase #7	$205.81	10.520%	$227.4612	$227.46	$227.45	$227.50
7 purchase totals =	$934.49		$1,016.7308	$1,016.73	$1,016.75	$1,016.70