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	$68.73	13.286%	$77.8615	$77.86	$77.85	$77.90
Purchase #2	$13.46	13.699%	$15.3039	$15.30	$15.30	$15.30
Purchase #3	$16.78	6.811%	$17.9229	$17.92	$17.90	$17.90
Purchase #4	$104.71	6.835%	$111.8669	$111.87	$111.85	$111.90
Purchase #5	$66.81	9.462%	$73.1316	$73.13	$73.15	$73.10
Purchase #6	$158.80	10.107%	$174.8499	$174.85	$174.85	$174.80
Purchase #7	$121.77	4.770%	$127.5784	$127.58	$127.60	$127.60
7 purchase totals =	$551.06		$598.5151	$598.51	$598.50	$598.50