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	$111.81	10.513%	$123.5646	$123.56	$123.55	$123.60
Purchase #2	$92.68	8.438%	$100.5003	$100.50	$100.50	$100.50
Purchase #3	$143.29	8.215%	$155.0613	$155.06	$155.05	$155.10
Purchase #4	$238.64	7.496%	$256.5285	$256.53	$256.55	$256.50
Purchase #5	$11.96	10.742%	$13.2447	$13.24	$13.25	$13.20
Purchase #6	$25.36	10.614%	$28.0517	$28.05	$28.05	$28.10
Purchase #7	$170.83	11.301%	$190.1355	$190.14	$190.15	$190.10
7 purchase totals =	$794.57		$867.0866	$867.08	$867.10	$867.10