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	$208.94	3.291%	$215.8162	$215.82	$215.80	$215.80
Purchase #2	$81.50	8.553%	$88.4707	$88.47	$88.45	$88.50
Purchase #3	$16.78	9.133%	$18.3125	$18.31	$18.30	$18.30
Purchase #4	$35.41	13.329%	$40.1298	$40.13	$40.15	$40.10
Purchase #5	$40.60	6.592%	$43.2764	$43.28	$43.30	$43.30
Purchase #6	$12.30	8.449%	$13.3392	$13.34	$13.35	$13.30
Purchase #7	$9.78	10.334%	$10.7907	$10.79	$10.80	$10.80
7 purchase totals =	$405.31		$430.1355	$430.14	$430.15	$430.10