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	$68.68	5.710%	$72.6016	$72.60	$72.60	$72.60
Purchase #2	$12.83	5.156%	$13.4915	$13.49	$13.50	$13.50
Purchase #3	$31.29	11.526%	$34.8965	$34.90	$34.90	$34.90
Purchase #4	$61.48	3.153%	$63.4185	$63.42	$63.40	$63.40
Purchase #5	$103.32	7.542%	$111.1124	$111.11	$111.10	$111.10
Purchase #6	$112.94	9.200%	$123.3305	$123.33	$123.35	$123.30
Purchase #7	$150.81	6.137%	$160.0652	$160.07	$160.05	$160.10
7 purchase totals =	$541.35		$578.9162	$578.92	$578.90	$578.90