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	$182.90	8.733%	$198.8727	$198.87	$198.85	$198.90
Purchase #2	$30.43	10.159%	$33.5214	$33.52	$33.50	$33.50
Purchase #3	$113.32	5.765%	$119.8529	$119.85	$119.85	$119.90
Purchase #4	$104.61	6.282%	$111.1816	$111.18	$111.20	$111.20
Purchase #5	$85.34	3.320%	$88.1733	$88.17	$88.15	$88.20
Purchase #6	$143.69	7.171%	$153.994	$153.99	$154.00	$154.00
Purchase #7	$110.93	13.640%	$126.0609	$126.06	$126.05	$126.10
7 purchase totals =	$771.22		$831.6568	$831.64	$831.60	$831.80