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	$61.59	13.222%	$69.7334	$69.73	$69.75	$69.70
Purchase #2	$51.82	11.661%	$57.8627	$57.86	$57.85	$57.90
Purchase #3	$57.97	11.546%	$64.6632	$64.66	$64.65	$64.70
Purchase #4	$166.80	7.661%	$179.5785	$179.58	$179.60	$179.60
Purchase #5	$59.73	4.241%	$62.2631	$62.26	$62.25	$62.30
Purchase #6	$61.86	6.699%	$66.004	$66.00	$66.00	$66.00
Purchase #7	$202.96	5.153%	$213.4185	$213.42	$213.40	$213.40
7 purchase totals =	$662.73		$713.5234	$713.51	$713.50	$713.60