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	$38.72	7.360%	$41.5698	$41.57	$41.55	$41.60
Purchase #2	$114.86	13.538%	$130.4097	$130.41	$130.40	$130.40
Purchase #3	$94.89	9.162%	$103.5838	$103.58	$103.60	$103.60
Purchase #4	$75.47	7.504%	$81.1333	$81.13	$81.15	$81.10
Purchase #5	$189.43	12.174%	$212.4912	$212.49	$212.50	$212.50
Purchase #6	$213.28	4.491%	$222.8584	$222.86	$222.85	$222.90
Purchase #7	$90.76	13.466%	$102.9817	$102.98	$103.00	$103.00
7 purchase totals =	$817.41		$895.0279	$895.02	$895.05	$895.10