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	$240.75	10.316%	$265.5858	$265.59	$265.60	$265.60
Purchase #2	$35.27	5.128%	$37.0786	$37.08	$37.10	$37.10
Purchase #3	$56.71	10.198%	$62.4933	$62.49	$62.50	$62.50
Purchase #4	$205.60	13.615%	$233.5924	$233.59	$233.60	$233.60
Purchase #5	$43.64	10.786%	$48.347	$48.35	$48.35	$48.30
Purchase #6	$183.89	10.190%	$202.6284	$202.63	$202.65	$202.60
Purchase #7	$28.87	11.174%	$32.0959	$32.10	$32.10	$32.10
7 purchase totals =	$794.73		$881.8214	$881.83	$881.90	$881.80