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	$219.76	11.554%	$245.1511	$245.15	$245.15	$245.20
Purchase #2	$175.84	9.334%	$192.2529	$192.25	$192.25	$192.30
Purchase #3	$115.66	10.679%	$128.0113	$128.01	$128.00	$128.00
Purchase #4	$112.99	9.598%	$123.8348	$123.83	$123.85	$123.80
Purchase #5	$27.36	4.103%	$28.4826	$28.48	$28.50	$28.50
Purchase #6	$117.32	12.544%	$132.0366	$132.04	$132.05	$132.00
Purchase #7	$19.52	5.127%	$20.5208	$20.52	$20.50	$20.50
7 purchase totals =	$788.45		$870.2901	$870.28	$870.30	$870.30