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	$17.42	9.817%	$19.1301	$19.13	$19.15	$19.10
Purchase #2	$159.47	10.712%	$176.5524	$176.55	$176.55	$176.60
Purchase #3	$9.73	4.557%	$10.1734	$10.17	$10.15	$10.20
Purchase #4	$20.97	3.828%	$21.7727	$21.77	$21.75	$21.80
Purchase #5	$112.72	3.293%	$116.4319	$116.43	$116.45	$116.40
Purchase #6	$92.73	10.598%	$102.5575	$102.56	$102.55	$102.60
Purchase #7	$158.67	5.405%	$167.2461	$167.25	$167.25	$167.20
7 purchase totals =	$571.71		$613.8641	$613.86	$613.85	$613.90