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	$89.98	11.845%	$100.6381	$100.64	$100.65	$100.60
Purchase #2	$147.80	11.373%	$164.6093	$164.61	$164.60	$164.60
Purchase #3	$198.77	3.528%	$205.7826	$205.78	$205.80	$205.80
Purchase #4	$123.93	10.235%	$136.6142	$136.61	$136.60	$136.60
Purchase #5	$43.93	9.754%	$48.2149	$48.21	$48.20	$48.20
Purchase #6	$32.43	11.182%	$36.0563	$36.06	$36.05	$36.10
Purchase #7	$219.45	10.162%	$241.7505	$241.75	$241.75	$241.80
7 purchase totals =	$856.29		$933.6659	$933.66	$933.65	$933.70