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	$61.46	8.266%	$66.5403	$66.54	$66.55	$66.50
Purchase #2	$16.30	8.543%	$17.6925	$17.69	$17.70	$17.70
Purchase #3	$129.30	7.761%	$139.335	$139.34	$139.35	$139.30
Purchase #4	$245.30	5.346%	$258.4137	$258.41	$258.40	$258.40
Purchase #5	$96.44	7.422%	$103.5978	$103.60	$103.60	$103.60
Purchase #6	$202.60	12.280%	$227.4793	$227.48	$227.50	$227.50
Purchase #7	$246.53	3.782%	$255.8538	$255.85	$255.85	$255.90
7 purchase totals =	$997.93		$1,068.9124	$1,068.91	$1,068.95	$1,068.90