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	$142.67	9.659%	$156.4505	$156.45	$156.45	$156.50
Purchase #2	$46.42	3.510%	$48.0493	$48.05	$48.05	$48.00
Purchase #3	$211.33	13.461%	$239.7771	$239.78	$239.80	$239.80
Purchase #4	$102.72	9.847%	$112.8348	$112.83	$112.85	$112.80
Purchase #5	$30.98	8.530%	$33.6226	$33.62	$33.60	$33.60
Purchase #6	$43.78	4.359%	$45.6884	$45.69	$45.70	$45.70
Purchase #7	$101.81	9.646%	$111.6306	$111.63	$111.65	$111.60
7 purchase totals =	$679.71		$748.0533	$748.05	$748.10	$748.00