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	$60.54	9.128%	$66.0661	$66.07	$66.05	$66.10
Purchase #2	$88.28	5.169%	$92.8432	$92.84	$92.85	$92.80
Purchase #3	$219.75	6.838%	$234.7765	$234.78	$234.80	$234.80
Purchase #4	$42.86	5.384%	$45.1676	$45.17	$45.15	$45.20
Purchase #5	$137.78	7.643%	$148.3105	$148.31	$148.30	$148.30
Purchase #6	$220.31	11.189%	$244.9605	$244.96	$244.95	$245.00
Purchase #7	$210.54	9.465%	$230.4676	$230.47	$230.45	$230.50
7 purchase totals =	$980.06		$1,062.5920	$1,062.60	$1,062.55	$1,062.70