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	$144.92	5.339%	$152.6573	$152.66	$152.65	$152.70
Purchase #2	$78.68	8.491%	$85.3607	$85.36	$85.35	$85.40
Purchase #3	$163.98	7.189%	$175.7685	$175.77	$175.75	$175.80
Purchase #4	$28.54	9.854%	$31.3523	$31.35	$31.35	$31.40
Purchase #5	$14.99	5.271%	$15.7801	$15.78	$15.80	$15.80
Purchase #6	$104.86	6.334%	$111.5018	$111.50	$111.50	$111.50
Purchase #7	$103.64	5.162%	$108.9899	$108.99	$109.00	$109.00
7 purchase totals =	$639.61		$681.4106	$681.41	$681.40	$681.60