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	$157.63	13.853%	$179.4665	$179.47	$179.45	$179.50
Purchase #2	$206.63	4.374%	$215.668	$215.67	$215.65	$215.70
Purchase #3	$87.45	6.201%	$92.8728	$92.87	$92.85	$92.90
Purchase #4	$112.82	13.820%	$128.4117	$128.41	$128.40	$128.40
Purchase #5	$75.44	13.462%	$85.5957	$85.60	$85.60	$85.60
Purchase #6	$163.72	5.309%	$172.4119	$172.41	$172.40	$172.40
Purchase #7	$117.42	13.153%	$132.8643	$132.86	$132.85	$132.90
7 purchase totals =	$921.11		$1,007.2909	$1,007.29	$1,007.20	$1,007.40