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	$121.75	9.296%	$133.0679	$133.07	$133.05	$133.10
Purchase #2	$19.43	10.795%	$21.5275	$21.53	$21.55	$21.50
Purchase #3	$65.44	10.194%	$72.111	$72.11	$72.10	$72.10
Purchase #4	$31.90	8.341%	$34.5608	$34.56	$34.55	$34.60
Purchase #5	$248.51	12.746%	$280.1851	$280.19	$280.20	$280.20
Purchase #6	$21.69	10.157%	$23.8931	$23.89	$23.90	$23.90
Purchase #7	$91.48	7.678%	$98.5038	$98.50	$98.50	$98.50
7 purchase totals =	$600.20		$663.8492	$663.85	$663.85	$663.90