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	$84.86	12.567%	$95.5244	$95.52	$95.50	$95.50
Purchase #2	$24.43	8.177%	$26.4276	$26.43	$26.45	$26.40
Purchase #3	$138.52	3.443%	$143.2892	$143.29	$143.30	$143.30
Purchase #4	$233.47	9.615%	$255.9181	$255.92	$255.90	$255.90
Purchase #5	$137.34	5.429%	$144.7962	$144.80	$144.80	$144.80
Purchase #6	$96.60	3.386%	$99.8709	$99.87	$99.85	$99.90
Purchase #7	$134.86	10.283%	$148.7277	$148.73	$148.75	$148.70
7 purchase totals =	$850.08		$914.5541	$914.56	$914.55	$914.50