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	$192.26	4.470%	$200.854	$200.85	$200.85	$200.90
Purchase #2	$146.38	6.517%	$155.9196	$155.92	$155.90	$155.90
Purchase #3	$162.40	13.189%	$183.8189	$183.82	$183.80	$183.80
Purchase #4	$34.41	10.361%	$37.9752	$37.98	$38.00	$38.00
Purchase #5	$186.83	6.618%	$199.1944	$199.19	$199.20	$199.20
Purchase #6	$66.66	6.302%	$70.8609	$70.86	$70.85	$70.90
Purchase #7	$191.89	4.392%	$200.3178	$200.32	$200.30	$200.30
7 purchase totals =	$980.83		$1,048.9408	$1,048.94	$1,048.90	$1,049.00