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	$128.93	4.621%	$134.8879	$134.89	$134.90	$134.90
Purchase #2	$19.56	6.461%	$20.8238	$20.82	$20.80	$20.80
Purchase #3	$10.85	5.172%	$11.4112	$11.41	$11.40	$11.40
Purchase #4	$84.43	3.652%	$87.5134	$87.51	$87.50	$87.50
Purchase #5	$93.39	13.119%	$105.6418	$105.64	$105.65	$105.60
Purchase #6	$65.45	10.344%	$72.2201	$72.22	$72.20	$72.20
Purchase #7	$128.95	3.859%	$133.9262	$133.93	$133.95	$133.90
7 purchase totals =	$531.56		$566.4244	$566.42	$566.40	$566.30