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	$241.59	8.549%	$262.2435	$262.24	$262.25	$262.20
Purchase #2	$244.56	4.326%	$255.1397	$255.14	$255.15	$255.10
Purchase #3	$238.89	13.223%	$270.4784	$270.48	$270.50	$270.50
Purchase #4	$230.52	9.671%	$252.8136	$252.81	$252.80	$252.80
Purchase #5	$111.62	10.203%	$123.0086	$123.01	$123.00	$123.00
Purchase #6	$78.60	6.704%	$83.8693	$83.87	$83.85	$83.90
Purchase #7	$201.31	6.611%	$214.6186	$214.62	$214.60	$214.60
7 purchase totals =	$1,347.09		$1,462.1717	$1,462.17	$1,462.15	$1,462.10