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	$145.77	11.449%	$162.4592	$162.46	$162.45	$162.50
Purchase #2	$107.29	12.617%	$120.8268	$120.83	$120.85	$120.80
Purchase #3	$157.70	6.431%	$167.8417	$167.84	$167.85	$167.80
Purchase #4	$180.67	5.516%	$190.6358	$190.64	$190.65	$190.60
Purchase #5	$188.32	11.736%	$210.4212	$210.42	$210.40	$210.40
Purchase #6	$51.64	9.591%	$56.5928	$56.59	$56.60	$56.60
Purchase #7	$151.74	10.730%	$168.0217	$168.02	$168.00	$168.00
7 purchase totals =	$983.13		$1,076.7992	$1,076.80	$1,076.80	$1,076.70