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	$76.64	13.593%	$87.0577	$87.06	$87.05	$87.10
Purchase #2	$117.96	5.285%	$124.1942	$124.19	$124.20	$124.20
Purchase #3	$164.39	4.302%	$171.4621	$171.46	$171.45	$171.50
Purchase #4	$126.38	12.406%	$142.0587	$142.06	$142.05	$142.10
Purchase #5	$66.38	6.706%	$70.8314	$70.83	$70.85	$70.80
Purchase #6	$221.32	5.653%	$233.8312	$233.83	$233.85	$233.80
Purchase #7	$191.53	11.466%	$213.4908	$213.49	$213.50	$213.50
7 purchase totals =	$964.60		$1,042.9261	$1,042.92	$1,042.95	$1,043.00