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	$213.95	6.790%	$228.4772	$228.48	$228.50	$228.50
Purchase #2	$235.95	9.134%	$257.5017	$257.50	$257.50	$257.50
Purchase #3	$199.31	12.342%	$223.9088	$223.91	$223.90	$223.90
Purchase #4	$120.94	13.802%	$137.6321	$137.63	$137.65	$137.60
Purchase #5	$182.96	12.549%	$205.9197	$205.92	$205.90	$205.90
Purchase #6	$13.66	12.660%	$15.3894	$15.39	$15.40	$15.40
Purchase #7	$12.25	3.423%	$12.6693	$12.67	$12.65	$12.70
7 purchase totals =	$979.02		$1,081.4982	$1,081.50	$1,081.50	$1,081.50