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	$208.43	4.256%	$217.3008	$217.30	$217.30	$217.30
Purchase #2	$158.93	8.612%	$172.6171	$172.62	$172.60	$172.60
Purchase #3	$96.28	8.358%	$104.3271	$104.33	$104.35	$104.30
Purchase #4	$208.92	6.397%	$222.2846	$222.28	$222.30	$222.30
Purchase #5	$160.33	13.622%	$182.1702	$182.17	$182.15	$182.20
Purchase #6	$97.68	6.299%	$103.8329	$103.83	$103.85	$103.80
Purchase #7	$28.56	9.804%	$31.36	$31.36	$31.35	$31.40
7 purchase totals =	$959.13		$1,033.8927	$1,033.89	$1,033.90	$1,033.90