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	$241.56	3.783%	$250.6982	$250.70	$250.70	$250.70
Purchase #2	$247.49	13.172%	$280.0894	$280.09	$280.10	$280.10
Purchase #3	$154.41	5.733%	$163.2623	$163.26	$163.25	$163.30
Purchase #4	$121.46	13.108%	$137.381	$137.38	$137.40	$137.40
Purchase #5	$27.44	13.155%	$31.0497	$31.05	$31.05	$31.00
Purchase #6	$83.31	8.382%	$90.293	$90.29	$90.30	$90.30
Purchase #7	$47.91	5.257%	$50.4286	$50.43	$50.45	$50.40
7 purchase totals =	$923.58		$1,003.2022	$1,003.20	$1,003.25	$1,003.20