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	$220.38	13.715%	$250.6051	$250.61	$250.60	$250.60
Purchase #2	$146.90	12.831%	$165.7487	$165.75	$165.75	$165.70
Purchase #3	$184.59	6.413%	$196.4278	$196.43	$196.45	$196.40
Purchase #4	$143.95	4.464%	$150.3759	$150.38	$150.40	$150.40
Purchase #5	$96.81	6.671%	$103.2682	$103.27	$103.25	$103.30
Purchase #6	$81.39	13.709%	$92.5478	$92.55	$92.55	$92.50
Purchase #7	$28.56	13.849%	$32.5153	$32.52	$32.50	$32.50
7 purchase totals =	$902.58		$991.4888	$991.51	$991.50	$991.40