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	$243.88	11.542%	$272.0286	$272.03	$272.05	$272.00
Purchase #2	$23.52	5.794%	$24.8827	$24.88	$24.90	$24.90
Purchase #3	$238.44	11.365%	$265.5387	$265.54	$265.55	$265.50
Purchase #4	$40.53	11.249%	$45.0892	$45.09	$45.10	$45.10
Purchase #5	$76.68	4.347%	$80.0133	$80.01	$80.00	$80.00
Purchase #6	$92.38	3.436%	$95.5542	$95.55	$95.55	$95.60
Purchase #7	$86.26	3.679%	$89.4335	$89.43	$89.45	$89.40
7 purchase totals =	$801.69		$872.5402	$872.53	$872.60	$872.50