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	$125.73	10.857%	$139.3805	$139.38	$139.40	$139.40
Purchase #2	$26.43	11.116%	$29.368	$29.37	$29.35	$29.40
Purchase #3	$238.45	13.526%	$270.7027	$270.70	$270.70	$270.70
Purchase #4	$132.51	6.555%	$141.196	$141.20	$141.20	$141.20
Purchase #5	$74.87	4.518%	$78.2526	$78.25	$78.25	$78.30
Purchase #6	$149.40	12.402%	$167.9286	$167.93	$167.95	$167.90
Purchase #7	$109.32	10.348%	$120.6324	$120.63	$120.65	$120.60
7 purchase totals =	$856.71		$947.4608	$947.46	$947.50	$947.50