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	$103.59	12.769%	$116.8174	$116.82	$116.80	$116.80
Purchase #2	$98.43	13.345%	$111.5655	$111.57	$111.55	$111.60
Purchase #3	$145.58	4.377%	$151.952	$151.95	$151.95	$152.00
Purchase #4	$51.35	12.420%	$57.7277	$57.73	$57.75	$57.70
Purchase #5	$60.99	4.269%	$63.5937	$63.59	$63.60	$63.60
Purchase #6	$46.55	11.845%	$52.0638	$52.06	$52.05	$52.10
Purchase #7	$102.99	8.660%	$111.9089	$111.91	$111.90	$111.90
7 purchase totals =	$609.48		$665.6290	$665.63	$665.60	$665.70