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	$208.25	11.294%	$231.7698	$231.77	$231.75	$231.80
Purchase #2	$45.71	5.155%	$48.0664	$48.07	$48.05	$48.10
Purchase #3	$236.90	10.635%	$262.0943	$262.09	$262.10	$262.10
Purchase #4	$92.60	4.228%	$96.5151	$96.52	$96.50	$96.50
Purchase #5	$78.92	12.197%	$88.5459	$88.55	$88.55	$88.50
Purchase #6	$12.64	7.576%	$13.5976	$13.60	$13.60	$13.60
Purchase #7	$123.90	6.245%	$131.6376	$131.64	$131.65	$131.60
7 purchase totals =	$798.92		$872.2267	$872.24	$872.20	$872.20