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	$172.70	9.595%	$189.2706	$189.27	$189.25	$189.30
Purchase #2	$57.73	10.643%	$63.8742	$63.87	$63.85	$63.90
Purchase #3	$11.35	4.572%	$11.8689	$11.87	$11.85	$11.90
Purchase #4	$127.61	13.113%	$144.3435	$144.34	$144.35	$144.30
Purchase #5	$51.25	11.798%	$57.2965	$57.30	$57.30	$57.30
Purchase #6	$128.48	6.718%	$137.1113	$137.11	$137.10	$137.10
Purchase #7	$237.25	7.741%	$255.6155	$255.62	$255.60	$255.60
7 purchase totals =	$786.37		$859.3805	$859.38	$859.30	$859.40