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	$230.76	3.465%	$238.7558	$238.76	$238.75	$238.80
Purchase #2	$81.62	7.625%	$87.8435	$87.84	$87.85	$87.80
Purchase #3	$105.74	5.599%	$111.6604	$111.66	$111.65	$111.70
Purchase #4	$141.32	7.763%	$152.2907	$152.29	$152.30	$152.30
Purchase #5	$158.26	12.496%	$178.0362	$178.04	$178.05	$178.00
Purchase #6	$92.64	12.113%	$103.8615	$103.86	$103.85	$103.90
Purchase #7	$95.82	12.803%	$108.0878	$108.09	$108.10	$108.10
7 purchase totals =	$906.16		$980.5359	$980.54	$980.55	$980.60