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	$110.43	6.808%	$117.9481	$117.95	$117.95	$117.90
Purchase #2	$55.67	10.321%	$61.4157	$61.42	$61.40	$61.40
Purchase #3	$63.58	4.246%	$66.2796	$66.28	$66.30	$66.30
Purchase #4	$82.26	9.383%	$89.9785	$89.98	$90.00	$90.00
Purchase #5	$63.31	3.177%	$65.3214	$65.32	$65.30	$65.30
Purchase #6	$9.92	8.800%	$10.793	$10.79	$10.80	$10.80
Purchase #7	$215.48	4.561%	$225.308	$225.31	$225.30	$225.30
7 purchase totals =	$600.65		$637.0443	$637.05	$637.05	$637.00