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	$100.71	8.452%	$109.222	$109.22	$109.20	$109.20
Purchase #2	$27.72	9.769%	$30.428	$30.43	$30.45	$30.40
Purchase #3	$117.38	5.125%	$123.3957	$123.40	$123.40	$123.40
Purchase #4	$174.55	9.648%	$191.3906	$191.39	$191.40	$191.40
Purchase #5	$163.76	5.564%	$172.8716	$172.87	$172.85	$172.90
Purchase #6	$42.42	12.699%	$47.8069	$47.81	$47.80	$47.80
Purchase #7	$202.83	12.110%	$227.3927	$227.39	$227.40	$227.40
7 purchase totals =	$829.37		$902.5075	$902.51	$902.50	$902.50