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	$214.54	8.867%	$233.5633	$233.56	$233.55	$233.60
Purchase #2	$245.43	11.661%	$274.0496	$274.05	$274.05	$274.00
Purchase #3	$190.82	9.352%	$208.6655	$208.67	$208.65	$208.70
Purchase #4	$37.93	7.478%	$40.7664	$40.77	$40.75	$40.80
Purchase #5	$60.75	5.131%	$63.8671	$63.87	$63.85	$63.90
Purchase #6	$54.81	4.108%	$57.0616	$57.06	$57.05	$57.10
Purchase #7	$82.60	8.583%	$89.6896	$89.69	$89.70	$89.70
7 purchase totals =	$886.88		$967.6631	$967.67	$967.60	$967.80