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	$60.99	9.768%	$66.9475	$66.95	$66.95	$66.90
Purchase #2	$27.69	12.638%	$31.1895	$31.19	$31.20	$31.20
Purchase #3	$217.27	11.556%	$242.3777	$242.38	$242.40	$242.40
Purchase #4	$122.96	7.435%	$132.1021	$132.10	$132.10	$132.10
Purchase #5	$35.85	11.657%	$40.029	$40.03	$40.05	$40.00
Purchase #6	$78.69	5.386%	$82.9282	$82.93	$82.95	$82.90
Purchase #7	$123.52	6.708%	$131.8057	$131.81	$131.80	$131.80
7 purchase totals =	$666.97		$727.3797	$727.39	$727.45	$727.30