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	$65.71	11.856%	$73.5006	$73.50	$73.50	$73.50
Purchase #2	$77.83	6.347%	$82.7699	$82.77	$82.75	$82.80
Purchase #3	$84.32	4.182%	$87.8463	$87.85	$87.85	$87.80
Purchase #4	$36.89	12.694%	$41.5728	$41.57	$41.55	$41.60
Purchase #5	$126.71	4.782%	$132.7693	$132.77	$132.75	$132.80
Purchase #6	$27.87	13.241%	$31.5603	$31.56	$31.55	$31.60
Purchase #7	$173.27	5.417%	$182.656	$182.66	$182.65	$182.70
7 purchase totals =	$592.60		$632.6752	$632.68	$632.60	$632.80