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	6.584%	$256.601	$256.60	$256.60	$256.60
Purchase #2	$38.90	10.196%	$42.8662	$42.87	$42.85	$42.90
Purchase #3	$85.39	8.807%	$92.9103	$92.91	$92.90	$92.90
Purchase #4	$51.40	10.481%	$56.7872	$56.79	$56.80	$56.80
Purchase #5	$232.75	6.124%	$247.0036	$247.00	$247.00	$247.00
Purchase #6	$60.81	4.572%	$63.5902	$63.59	$63.60	$63.60
Purchase #7	$140.75	8.335%	$152.4815	$152.48	$152.50	$152.50
7 purchase totals =	$850.75		$912.2400	$912.24	$912.25	$912.30