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	$228.50	8.329%	$247.5318	$247.53	$247.55	$247.50
Purchase #2	$213.53	3.230%	$220.427	$220.43	$220.45	$220.40
Purchase #3	$143.34	9.497%	$156.953	$156.95	$156.95	$157.00
Purchase #4	$120.97	5.733%	$127.9052	$127.91	$127.90	$127.90
Purchase #5	$25.32	7.845%	$27.3064	$27.31	$27.30	$27.30
Purchase #6	$97.94	3.678%	$101.5422	$101.54	$101.55	$101.50
Purchase #7	$101.49	9.505%	$111.1366	$111.14	$111.15	$111.10
7 purchase totals =	$931.09		$992.8022	$992.81	$992.85	$992.70