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	$225.74	13.119%	$255.3548	$255.35	$255.35	$255.40
Purchase #2	$61.75	5.325%	$65.0382	$65.04	$65.05	$65.00
Purchase #3	$167.30	4.634%	$175.0527	$175.05	$175.05	$175.10
Purchase #4	$116.83	13.510%	$132.6137	$132.61	$132.60	$132.60
Purchase #5	$42.48	7.258%	$45.5632	$45.56	$45.55	$45.60
Purchase #6	$162.76	13.733%	$185.1118	$185.11	$185.10	$185.10
Purchase #7	$126.66	8.229%	$137.0829	$137.08	$137.10	$137.10
7 purchase totals =	$903.52		$995.8173	$995.80	$995.80	$995.90