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	$193.46	12.667%	$217.9656	$217.97	$217.95	$218.00
Purchase #2	$142.30	6.824%	$152.0106	$152.01	$152.00	$152.00
Purchase #3	$36.66	12.510%	$41.2462	$41.25	$41.25	$41.20
Purchase #4	$227.84	10.197%	$251.0728	$251.07	$251.05	$251.10
Purchase #5	$40.60	3.821%	$42.1513	$42.15	$42.15	$42.20
Purchase #6	$125.57	4.716%	$131.4919	$131.49	$131.50	$131.50
Purchase #7	$100.98	3.819%	$104.8364	$104.84	$104.85	$104.80
7 purchase totals =	$867.41		$940.7748	$940.78	$940.75	$940.80