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	$65.54	10.828%	$72.6367	$72.64	$72.65	$72.60
Purchase #2	$117.29	5.414%	$123.6401	$123.64	$123.65	$123.60
Purchase #3	$125.69	5.620%	$132.7538	$132.75	$132.75	$132.80
Purchase #4	$172.31	6.573%	$183.6359	$183.64	$183.65	$183.60
Purchase #5	$197.73	9.185%	$215.8915	$215.89	$215.90	$215.90
Purchase #6	$102.83	13.261%	$116.4663	$116.47	$116.45	$116.50
Purchase #7	$92.49	6.521%	$98.5213	$98.52	$98.50	$98.50
7 purchase totals =	$873.88		$943.5456	$943.55	$943.55	$943.50