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	$43.91	10.791%	$48.6483	$48.65	$48.65	$48.60
Purchase #2	$35.98	5.809%	$38.0701	$38.07	$38.05	$38.10
Purchase #3	$156.98	7.335%	$168.4945	$168.49	$168.50	$168.50
Purchase #4	$20.66	4.702%	$21.6314	$21.63	$21.65	$21.60
Purchase #5	$40.72	11.630%	$45.4557	$45.46	$45.45	$45.50
Purchase #6	$58.68	13.349%	$66.5132	$66.51	$66.50	$66.50
Purchase #7	$115.41	11.584%	$128.7791	$128.78	$128.80	$128.80
7 purchase totals =	$472.34		$517.5923	$517.59	$517.60	$517.60