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	$247.95	7.127%	$265.6214	$265.62	$265.60	$265.60
Purchase #2	$217.63	9.751%	$238.8511	$238.85	$238.85	$238.90
Purchase #3	$196.27	3.668%	$203.4692	$203.47	$203.45	$203.50
Purchase #4	$135.85	4.706%	$142.2431	$142.24	$142.25	$142.20
Purchase #5	$127.61	10.822%	$141.42	$141.42	$141.40	$141.40
Purchase #6	$87.72	5.248%	$92.3235	$92.32	$92.30	$92.30
Purchase #7	$117.75	12.823%	$132.8491	$132.85	$132.85	$132.80
7 purchase totals =	$1,130.78		$1,216.7774	$1,216.77	$1,216.70	$1,216.70