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	$41.54	4.174%	$43.2739	$43.27	$43.25	$43.30
Purchase #2	$56.78	10.780%	$62.9009	$62.90	$62.90	$62.90
Purchase #3	$187.28	9.775%	$205.5866	$205.59	$205.60	$205.60
Purchase #4	$114.53	10.737%	$126.8271	$126.83	$126.85	$126.80
Purchase #5	$12.92	13.472%	$14.6606	$14.66	$14.65	$14.70
Purchase #6	$136.89	3.799%	$142.0905	$142.09	$142.10	$142.10
Purchase #7	$92.86	12.293%	$104.2753	$104.28	$104.30	$104.30
7 purchase totals =	$642.80		$699.6149	$699.62	$699.65	$699.70