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	$141.60	8.760%	$154.0042	$154.00	$154.00	$154.00
Purchase #2	$63.25	5.705%	$66.8584	$66.86	$66.85	$66.90
Purchase #3	$193.29	13.553%	$219.4866	$219.49	$219.50	$219.50
Purchase #4	$193.57	13.556%	$219.8103	$219.81	$219.80	$219.80
Purchase #5	$67.70	7.103%	$72.5087	$72.51	$72.50	$72.50
Purchase #6	$166.89	12.299%	$187.4158	$187.42	$187.40	$187.40
Purchase #7	$46.35	9.673%	$50.8334	$50.83	$50.85	$50.80
7 purchase totals =	$872.65		$970.9174	$970.92	$970.90	$970.90