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	$120.85	5.426%	$127.4073	$127.41	$127.40	$127.40
Purchase #2	$205.54	4.842%	$215.4922	$215.49	$215.50	$215.50
Purchase #3	$136.97	11.836%	$153.1818	$153.18	$153.20	$153.20
Purchase #4	$98.46	7.701%	$106.0424	$106.04	$106.05	$106.00
Purchase #5	$86.69	8.800%	$94.3187	$94.32	$94.30	$94.30
Purchase #6	$177.84	12.733%	$200.4844	$200.48	$200.50	$200.50
Purchase #7	$153.94	10.837%	$170.6225	$170.62	$170.60	$170.60
7 purchase totals =	$980.29		$1,067.5493	$1,067.54	$1,067.55	$1,067.50