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	$54.65	8.435%	$59.2597	$59.26	$59.25	$59.30
Purchase #2	$39.27	8.172%	$42.4791	$42.48	$42.50	$42.50
Purchase #3	$17.48	10.613%	$19.3352	$19.34	$19.35	$19.30
Purchase #4	$28.73	12.383%	$32.2876	$32.29	$32.30	$32.30
Purchase #5	$112.59	6.390%	$119.7845	$119.78	$119.80	$119.80
Purchase #6	$205.92	9.554%	$225.5936	$225.59	$225.60	$225.60
Purchase #7	$84.81	3.631%	$87.8895	$87.89	$87.90	$87.90
7 purchase totals =	$543.45		$586.6292	$586.63	$586.70	$586.70