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	$64.96	5.474%	$68.5159	$68.52	$68.50	$68.50
Purchase #2	$118.93	11.492%	$132.5974	$132.60	$132.60	$132.60
Purchase #3	$68.41	5.718%	$72.3217	$72.32	$72.30	$72.30
Purchase #4	$125.91	4.153%	$131.139	$131.14	$131.15	$131.10
Purchase #5	$172.98	8.404%	$187.5172	$187.52	$187.50	$187.50
Purchase #6	$118.65	6.337%	$126.1689	$126.17	$126.15	$126.20
Purchase #7	$83.45	13.419%	$94.6482	$94.65	$94.65	$94.60
7 purchase totals =	$753.29		$812.9083	$812.92	$812.85	$812.80