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	$132.74	9.673%	$145.5799	$145.58	$145.60	$145.60
Purchase #2	$100.79	8.383%	$109.2392	$109.24	$109.25	$109.20
Purchase #3	$111.30	6.548%	$118.5879	$118.59	$118.60	$118.60
Purchase #4	$105.98	3.125%	$109.2919	$109.29	$109.30	$109.30
Purchase #5	$87.95	11.384%	$97.9622	$97.96	$97.95	$98.00
Purchase #6	$63.36	7.123%	$67.8731	$67.87	$67.85	$67.90
Purchase #7	$87.92	3.388%	$90.8987	$90.90	$90.90	$90.90
7 purchase totals =	$690.04		$739.4329	$739.43	$739.45	$739.50