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	$128.43	4.208%	$133.8343	$133.83	$133.85	$133.80
Purchase #2	$139.73	3.467%	$144.5744	$144.57	$144.55	$144.60
Purchase #3	$89.52	8.708%	$97.3154	$97.32	$97.30	$97.30
Purchase #4	$157.37	11.477%	$175.4314	$175.43	$175.45	$175.40
Purchase #5	$24.73	11.720%	$27.6284	$27.63	$27.65	$27.60
Purchase #6	$225.45	8.854%	$245.4113	$245.41	$245.40	$245.40
Purchase #7	$144.88	6.616%	$154.4653	$154.47	$154.45	$154.50
7 purchase totals =	$910.11		$978.6605	$978.66	$978.65	$978.60