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	$100.89	6.486%	$107.4337	$107.43	$107.45	$107.40
Purchase #2	$167.62	9.513%	$183.5657	$183.57	$183.55	$183.60
Purchase #3	$117.72	5.659%	$124.3818	$124.38	$124.40	$124.40
Purchase #4	$181.59	8.232%	$196.5385	$196.54	$196.55	$196.50
Purchase #5	$185.71	10.846%	$205.8521	$205.85	$205.85	$205.90
Purchase #6	$14.95	5.734%	$15.8072	$15.81	$15.80	$15.80
Purchase #7	$35.84	4.439%	$37.4309	$37.43	$37.45	$37.40
7 purchase totals =	$804.32		$871.0099	$871.01	$871.05	$871.00