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	$166.82	12.290%	$187.3222	$187.32	$187.30	$187.30
Purchase #2	$162.66	13.672%	$184.8989	$184.90	$184.90	$184.90
Purchase #3	$50.46	9.202%	$55.1033	$55.10	$55.10	$55.10
Purchase #4	$127.88	3.186%	$131.9543	$131.95	$131.95	$132.00
Purchase #5	$247.77	13.212%	$280.5054	$280.51	$280.50	$280.50
Purchase #6	$153.58	4.108%	$159.8891	$159.89	$159.90	$159.90
Purchase #7	$124.46	7.341%	$133.5966	$133.60	$133.60	$133.60
7 purchase totals =	$1,033.63		$1,133.2698	$1,133.27	$1,133.25	$1,133.30