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	$8.95	6.800%	$9.5586	$9.56	$9.55	$9.60
Purchase #2	$136.53	5.757%	$144.39	$144.39	$144.40	$144.40
Purchase #3	$26.59	11.276%	$29.5883	$29.59	$29.60	$29.60
Purchase #4	$208.95	6.174%	$221.8506	$221.85	$221.85	$221.90
Purchase #5	$98.41	5.138%	$103.4663	$103.47	$103.45	$103.50
Purchase #6	$72.78	7.606%	$78.3156	$78.32	$78.30	$78.30
Purchase #7	$163.47	6.669%	$174.3718	$174.37	$174.35	$174.40
7 purchase totals =	$715.68		$761.5412	$761.55	$761.50	$761.70