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	$99.55	12.262%	$111.7568	$111.76	$111.75	$111.80
Purchase #2	$176.85	5.528%	$186.6263	$186.63	$186.65	$186.60
Purchase #3	$15.97	10.236%	$17.6047	$17.60	$17.60	$17.60
Purchase #4	$30.31	7.222%	$32.499	$32.50	$32.50	$32.50
Purchase #5	$71.86	13.121%	$81.2888	$81.29	$81.30	$81.30
Purchase #6	$131.94	9.795%	$144.8635	$144.86	$144.85	$144.90
Purchase #7	$126.41	8.410%	$137.0411	$137.04	$137.05	$137.00
7 purchase totals =	$652.89		$711.6802	$711.68	$711.70	$711.70