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	$164.76	13.307%	$186.6846	$186.68	$186.70	$186.70
Purchase #2	$196.70	12.844%	$221.9641	$221.96	$221.95	$222.00
Purchase #3	$50.85	3.560%	$52.6603	$52.66	$52.65	$52.70
Purchase #4	$208.25	7.811%	$224.5164	$224.52	$224.50	$224.50
Purchase #5	$27.60	4.659%	$28.8859	$28.89	$28.90	$28.90
Purchase #6	$100.25	4.204%	$104.4645	$104.46	$104.45	$104.50
Purchase #7	$198.78	10.604%	$219.8586	$219.86	$219.85	$219.90
7 purchase totals =	$947.19		$1,039.0344	$1,039.03	$1,039.00	$1,039.20