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	$222.84	5.230%	$234.4945	$234.49	$234.50	$234.50
Purchase #2	$76.48	12.319%	$85.9016	$85.90	$85.90	$85.90
Purchase #3	$135.40	5.749%	$143.1841	$143.18	$143.20	$143.20
Purchase #4	$39.82	10.113%	$43.847	$43.85	$43.85	$43.80
Purchase #5	$43.49	6.858%	$46.4725	$46.47	$46.45	$46.50
Purchase #6	$87.87	8.208%	$95.0824	$95.08	$95.10	$95.10
Purchase #7	$81.68	5.872%	$86.4762	$86.48	$86.50	$86.50
7 purchase totals =	$687.58		$735.4583	$735.45	$735.50	$735.50