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	$238.88	7.316%	$256.3565	$256.36	$256.35	$256.40
Purchase #2	$31.78	11.383%	$35.3975	$35.40	$35.40	$35.40
Purchase #3	$51.49	11.365%	$57.3418	$57.34	$57.35	$57.30
Purchase #4	$17.89	12.716%	$20.1649	$20.16	$20.15	$20.20
Purchase #5	$14.47	5.555%	$15.2738	$15.27	$15.25	$15.30
Purchase #6	$30.95	10.360%	$34.1564	$34.16	$34.15	$34.20
Purchase #7	$50.30	4.308%	$52.4669	$52.47	$52.45	$52.50
7 purchase totals =	$435.76		$471.1578	$471.16	$471.10	$471.30