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	$146.45	5.503%	$154.5091	$154.51	$154.50	$154.50
Purchase #2	$63.28	12.136%	$70.9597	$70.96	$70.95	$71.00
Purchase #3	$15.51	6.734%	$16.5544	$16.55	$16.55	$16.60
Purchase #4	$165.45	5.504%	$174.5564	$174.56	$174.55	$174.60
Purchase #5	$49.78	6.254%	$52.8932	$52.89	$52.90	$52.90
Purchase #6	$95.93	10.271%	$105.783	$105.78	$105.80	$105.80
Purchase #7	$115.89	8.321%	$125.5332	$125.53	$125.55	$125.50
7 purchase totals =	$652.29		$700.7890	$700.78	$700.80	$700.90