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	$223.73	3.522%	$231.6098	$231.61	$231.60	$231.60
Purchase #2	$28.80	10.661%	$31.8704	$31.87	$31.85	$31.90
Purchase #3	$127.75	13.484%	$144.9758	$144.98	$145.00	$145.00
Purchase #4	$31.68	8.643%	$34.4181	$34.42	$34.40	$34.40
Purchase #5	$24.43	13.798%	$27.8009	$27.80	$27.80	$27.80
Purchase #6	$95.91	4.195%	$99.9334	$99.93	$99.95	$99.90
Purchase #7	$128.92	10.698%	$142.7119	$142.71	$142.70	$142.70
7 purchase totals =	$661.22		$713.3203	$713.32	$713.30	$713.30