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	$100.38	3.475%	$103.8682	$103.87	$103.85	$103.90
Purchase #2	$125.63	5.558%	$132.6125	$132.61	$132.60	$132.60
Purchase #3	$191.35	11.239%	$212.8558	$212.86	$212.85	$212.90
Purchase #4	$108.64	7.185%	$116.4458	$116.45	$116.45	$116.40
Purchase #5	$208.82	6.449%	$222.2868	$222.29	$222.30	$222.30
Purchase #6	$72.85	12.854%	$82.2141	$82.21	$82.20	$82.20
Purchase #7	$217.26	8.526%	$235.7836	$235.78	$235.80	$235.80
7 purchase totals =	$1,024.93		$1,106.0668	$1,106.07	$1,106.05	$1,106.10