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	$77.69	7.377%	$83.4212	$83.42	$83.40	$83.40
Purchase #2	$60.68	13.482%	$68.8609	$68.86	$68.85	$68.90
Purchase #3	$76.75	7.627%	$82.6037	$82.60	$82.60	$82.60
Purchase #4	$68.98	11.520%	$76.9265	$76.93	$76.95	$76.90
Purchase #5	$99.84	11.464%	$111.2857	$111.29	$111.30	$111.30
Purchase #6	$140.79	12.283%	$158.0832	$158.08	$158.10	$158.10
Purchase #7	$145.62	11.806%	$162.8119	$162.81	$162.80	$162.80
7 purchase totals =	$670.35		$743.9931	$743.99	$744.00	$744.00