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	$202.86	5.259%	$213.5284	$213.53	$213.55	$213.50
Purchase #2	$91.86	12.697%	$103.5235	$103.52	$103.50	$103.50
Purchase #3	$190.82	12.149%	$214.0027	$214.00	$214.00	$214.00
Purchase #4	$122.34	7.487%	$131.4996	$131.50	$131.50	$131.50
Purchase #5	$7.64	5.492%	$8.0596	$8.06	$8.05	$8.10
Purchase #6	$166.55	10.198%	$183.5348	$183.53	$183.55	$183.50
Purchase #7	$105.43	6.599%	$112.3873	$112.39	$112.40	$112.40
7 purchase totals =	$887.50		$966.5359	$966.53	$966.55	$966.50