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	$198.66	9.277%	$217.0897	$217.09	$217.10	$217.10
Purchase #2	$151.55	4.421%	$158.25	$158.25	$158.25	$158.30
Purchase #3	$100.71	6.148%	$106.9017	$106.90	$106.90	$106.90
Purchase #4	$95.64	3.325%	$98.82	$98.82	$98.80	$98.80
Purchase #5	$98.89	5.356%	$104.1865	$104.19	$104.20	$104.20
Purchase #6	$72.75	11.779%	$81.3192	$81.32	$81.30	$81.30
Purchase #7	$109.78	3.859%	$114.0164	$114.02	$114.00	$114.00
7 purchase totals =	$827.98		$880.5835	$880.59	$880.55	$880.60