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	$56.52	10.603%	$62.5128	$62.51	$62.50	$62.50
Purchase #2	$21.89	3.466%	$22.6487	$22.65	$22.65	$22.60
Purchase #3	$32.41	11.202%	$36.0406	$36.04	$36.05	$36.00
Purchase #4	$176.97	13.349%	$200.5937	$200.59	$200.60	$200.60
Purchase #5	$68.70	4.648%	$71.8932	$71.89	$71.90	$71.90
Purchase #6	$33.60	8.816%	$36.5622	$36.56	$36.55	$36.60
Purchase #7	$230.72	10.640%	$255.2686	$255.27	$255.25	$255.30
7 purchase totals =	$620.81		$685.5198	$685.51	$685.50	$685.50