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	$157.94	8.585%	$171.4991	$171.50	$171.50	$171.50
Purchase #2	$204.38	9.861%	$224.5339	$224.53	$224.55	$224.50
Purchase #3	$239.93	13.189%	$271.5744	$271.57	$271.55	$271.60
Purchase #4	$41.30	5.559%	$43.5959	$43.60	$43.60	$43.60
Purchase #5	$114.78	10.675%	$127.0328	$127.03	$127.05	$127.00
Purchase #6	$29.58	12.874%	$33.3881	$33.39	$33.40	$33.40
Purchase #7	$167.54	3.116%	$172.7605	$172.76	$172.75	$172.80
7 purchase totals =	$955.45		$1,044.3847	$1,044.38	$1,044.40	$1,044.40