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	$211.83	4.578%	$221.5276	$221.53	$221.55	$221.50
Purchase #2	$38.35	13.491%	$43.5238	$43.52	$43.50	$43.50
Purchase #3	$70.78	6.111%	$75.1054	$75.11	$75.10	$75.10
Purchase #4	$109.38	9.518%	$119.7908	$119.79	$119.80	$119.80
Purchase #5	$103.85	3.483%	$107.4671	$107.47	$107.45	$107.50
Purchase #6	$12.37	11.622%	$13.8076	$13.81	$13.80	$13.80
Purchase #7	$222.86	5.297%	$234.6649	$234.66	$234.65	$234.70
7 purchase totals =	$769.42		$815.8872	$815.89	$815.85	$815.90