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	$132.57	10.427%	$146.3931	$146.39	$146.40	$146.40
Purchase #2	$174.29	7.770%	$187.8323	$187.83	$187.85	$187.80
Purchase #3	$47.87	6.161%	$50.8193	$50.82	$50.80	$50.80
Purchase #4	$95.81	3.500%	$99.1634	$99.16	$99.15	$99.20
Purchase #5	$115.60	6.585%	$123.2123	$123.21	$123.20	$123.20
Purchase #6	$186.90	11.379%	$208.1674	$208.17	$208.15	$208.20
Purchase #7	$184.88	8.563%	$200.7113	$200.71	$200.70	$200.70
7 purchase totals =	$937.92		$1,016.2991	$1,016.29	$1,016.25	$1,016.30