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	$100.39	12.185%	$112.6225	$112.62	$112.60	$112.60
Purchase #2	$191.66	13.285%	$217.122	$217.12	$217.10	$217.10
Purchase #3	$40.70	11.525%	$45.3907	$45.39	$45.40	$45.40
Purchase #4	$218.34	13.397%	$247.591	$247.59	$247.60	$247.60
Purchase #5	$63.99	4.700%	$66.9975	$67.00	$67.00	$67.00
Purchase #6	$188.86	12.221%	$211.9406	$211.94	$211.95	$211.90
Purchase #7	$95.56	7.638%	$102.8589	$102.86	$102.85	$102.90
7 purchase totals =	$899.50		$1,004.5232	$1,004.52	$1,004.50	$1,004.50