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	$96.55	12.324%	$108.4488	$108.45	$108.45	$108.40
Purchase #2	$145.98	8.183%	$157.9255	$157.93	$157.95	$157.90
Purchase #3	$38.38	10.799%	$42.5247	$42.52	$42.50	$42.50
Purchase #4	$112.76	8.856%	$122.746	$122.75	$122.75	$122.70
Purchase #5	$95.49	5.133%	$100.3915	$100.39	$100.40	$100.40
Purchase #6	$132.34	9.797%	$145.3053	$145.31	$145.30	$145.30
Purchase #7	$132.93	3.406%	$137.4576	$137.46	$137.45	$137.50
7 purchase totals =	$754.43		$814.7994	$814.81	$814.80	$814.70