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	$118.67	4.337%	$123.8167	$123.82	$123.80	$123.80
Purchase #2	$145.41	13.407%	$164.9051	$164.91	$164.90	$164.90
Purchase #3	$41.83	3.641%	$43.353	$43.35	$43.35	$43.40
Purchase #4	$126.46	3.735%	$131.1833	$131.18	$131.20	$131.20
Purchase #5	$10.60	13.817%	$12.0646	$12.06	$12.05	$12.10
Purchase #6	$178.65	7.715%	$192.4328	$192.43	$192.45	$192.40
Purchase #7	$199.77	13.557%	$226.8528	$226.85	$226.85	$226.90
7 purchase totals =	$821.39		$894.6083	$894.60	$894.60	$894.70