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	$109.43	6.312%	$116.3372	$116.34	$116.35	$116.30
Purchase #2	$214.45	12.661%	$241.6015	$241.60	$241.60	$241.60
Purchase #3	$125.82	11.833%	$140.7083	$140.71	$140.70	$140.70
Purchase #4	$48.75	12.549%	$54.8676	$54.87	$54.85	$54.90
Purchase #5	$42.78	7.522%	$45.9979	$46.00	$46.00	$46.00
Purchase #6	$40.88	11.162%	$45.443	$45.44	$45.45	$45.40
Purchase #7	$93.25	9.729%	$102.3223	$102.32	$102.30	$102.30
7 purchase totals =	$675.36		$747.2778	$747.28	$747.25	$747.20