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	$103.52	7.404%	$111.1846	$111.18	$111.20	$111.20
Purchase #2	$59.37	6.153%	$63.023	$63.02	$63.00	$63.00
Purchase #3	$20.39	12.278%	$22.8935	$22.89	$22.90	$22.90
Purchase #4	$217.30	8.854%	$236.5397	$236.54	$236.55	$236.50
Purchase #5	$85.69	13.583%	$97.3293	$97.33	$97.35	$97.30
Purchase #6	$132.50	5.421%	$139.6828	$139.68	$139.70	$139.70
Purchase #7	$49.39	10.572%	$54.6115	$54.61	$54.60	$54.60
7 purchase totals =	$668.16		$725.2644	$725.25	$725.30	$725.20