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	$156.50	6.660%	$166.9229	$166.92	$166.90	$166.90
Purchase #2	$13.34	4.531%	$13.9444	$13.94	$13.95	$13.90
Purchase #3	$14.78	3.696%	$15.3263	$15.33	$15.35	$15.30
Purchase #4	$48.63	6.584%	$51.8318	$51.83	$51.85	$51.80
Purchase #5	$26.85	3.644%	$27.8284	$27.83	$27.85	$27.80
Purchase #6	$229.59	11.148%	$255.1847	$255.18	$255.20	$255.20
Purchase #7	$144.46	7.256%	$154.942	$154.94	$154.95	$154.90
7 purchase totals =	$634.15		$685.9805	$685.97	$686.05	$685.80