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	$205.45	9.440%	$224.8445	$224.84	$224.85	$224.80
Purchase #2	$164.81	13.139%	$186.4644	$186.46	$186.45	$186.50
Purchase #3	$179.29	4.763%	$187.8296	$187.83	$187.85	$187.80
Purchase #4	$105.52	11.620%	$117.7814	$117.78	$117.80	$117.80
Purchase #5	$105.73	12.376%	$118.8151	$118.82	$118.80	$118.80
Purchase #6	$169.60	11.468%	$189.0497	$189.05	$189.05	$189.00
Purchase #7	$76.77	5.387%	$80.9056	$80.91	$80.90	$80.90
7 purchase totals =	$1,007.17		$1,105.6903	$1,105.69	$1,105.70	$1,105.60