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	$106.46	9.294%	$116.3544	$116.35	$116.35	$116.40
Purchase #2	$145.57	10.817%	$161.3163	$161.32	$161.30	$161.30
Purchase #3	$82.71	7.649%	$89.0365	$89.04	$89.05	$89.00
Purchase #4	$20.72	5.160%	$21.7892	$21.79	$21.80	$21.80
Purchase #5	$15.27	5.647%	$16.1323	$16.13	$16.15	$16.10
Purchase #6	$159.80	8.734%	$173.7569	$173.76	$173.75	$173.80
Purchase #7	$179.25	3.296%	$185.1581	$185.16	$185.15	$185.20
7 purchase totals =	$709.78		$763.5437	$763.55	$763.55	$763.60