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	$126.71	11.551%	$141.3463	$141.35	$141.35	$141.30
Purchase #2	$71.38	12.156%	$80.057	$80.06	$80.05	$80.10
Purchase #3	$92.87	4.429%	$96.9832	$96.98	$97.00	$97.00
Purchase #4	$95.35	8.517%	$103.471	$103.47	$103.45	$103.50
Purchase #5	$20.85	4.246%	$21.7353	$21.74	$21.75	$21.70
Purchase #6	$137.84	10.600%	$152.451	$152.45	$152.45	$152.50
Purchase #7	$32.78	5.384%	$34.5449	$34.54	$34.55	$34.50
7 purchase totals =	$577.78		$630.5887	$630.59	$630.60	$630.60