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	$133.26	12.709%	$150.196	$150.20	$150.20	$150.20
Purchase #2	$46.34	8.203%	$50.1413	$50.14	$50.15	$50.10
Purchase #3	$107.87	3.733%	$111.8968	$111.90	$111.90	$111.90
Purchase #4	$19.70	4.140%	$20.5156	$20.52	$20.50	$20.50
Purchase #5	$188.34	5.454%	$198.6121	$198.61	$198.60	$198.60
Purchase #6	$136.89	12.426%	$153.9	$153.90	$153.90	$153.90
Purchase #7	$18.82	4.686%	$19.7019	$19.70	$19.70	$19.70
7 purchase totals =	$651.22		$704.9637	$704.97	$704.95	$704.90