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	$120.45	10.390%	$132.9648	$132.96	$132.95	$133.00
Purchase #2	$15.25	13.490%	$17.3072	$17.31	$17.30	$17.30
Purchase #3	$78.44	13.500%	$89.0294	$89.03	$89.05	$89.00
Purchase #4	$45.83	13.773%	$52.1422	$52.14	$52.15	$52.10
Purchase #5	$12.60	11.799%	$14.0867	$14.09	$14.10	$14.10
Purchase #6	$47.55	6.797%	$50.782	$50.78	$50.80	$50.80
Purchase #7	$103.80	12.473%	$116.747	$116.75	$116.75	$116.70
7 purchase totals =	$423.92		$473.0593	$473.06	$473.10	$473.00