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	$28.92	10.184%	$31.8652	$31.87	$31.85	$31.90
Purchase #2	$45.55	3.748%	$47.2572	$47.26	$47.25	$47.30
Purchase #3	$100.55	12.301%	$112.9187	$112.92	$112.90	$112.90
Purchase #4	$193.95	9.233%	$211.8574	$211.86	$211.85	$211.90
Purchase #5	$75.32	4.103%	$78.4104	$78.41	$78.40	$78.40
Purchase #6	$48.34	6.426%	$51.4463	$51.45	$51.45	$51.40
Purchase #7	$188.81	5.829%	$199.8157	$199.82	$199.80	$199.80
7 purchase totals =	$681.44		$733.5709	$733.59	$733.50	$733.60