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	$190.45	13.208%	$215.6046	$215.60	$215.60	$215.60
Purchase #2	$81.53	7.431%	$87.5885	$87.59	$87.60	$87.60
Purchase #3	$16.71	10.562%	$18.4749	$18.47	$18.45	$18.50
Purchase #4	$94.90	7.562%	$102.0763	$102.08	$102.10	$102.10
Purchase #5	$20.59	8.180%	$22.2743	$22.27	$22.25	$22.30
Purchase #6	$53.34	5.716%	$56.3889	$56.39	$56.40	$56.40
Purchase #7	$91.88	7.169%	$98.4669	$98.47	$98.45	$98.50
7 purchase totals =	$549.40		$600.8744	$600.87	$600.85	$601.00