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	$241.39	4.469%	$252.1777	$252.18	$252.20	$252.20
Purchase #2	$126.81	3.712%	$131.5172	$131.52	$131.50	$131.50
Purchase #3	$52.47	9.529%	$57.4699	$57.47	$57.45	$57.50
Purchase #4	$166.89	6.155%	$177.1621	$177.16	$177.15	$177.20
Purchase #5	$190.76	4.646%	$199.6227	$199.62	$199.60	$199.60
Purchase #6	$107.52	4.128%	$111.9584	$111.96	$111.95	$112.00
Purchase #7	$36.68	10.270%	$40.447	$40.45	$40.45	$40.40
7 purchase totals =	$922.52		$970.3550	$970.36	$970.30	$970.40