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	$12.86	11.336%	$14.3178	$14.32	$14.30	$14.30
Purchase #2	$84.43	8.110%	$91.2773	$91.28	$91.30	$91.30
Purchase #3	$140.46	12.619%	$158.1846	$158.18	$158.20	$158.20
Purchase #4	$231.56	8.209%	$250.5688	$250.57	$250.55	$250.60
Purchase #5	$94.89	4.853%	$99.495	$99.50	$99.50	$99.50
Purchase #6	$196.59	10.797%	$217.8158	$217.82	$217.80	$217.80
Purchase #7	$70.75	9.308%	$77.3354	$77.34	$77.35	$77.30
7 purchase totals =	$831.54		$908.9947	$909.01	$909.00	$909.00