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	$63.33	10.427%	$69.9334	$69.93	$69.95	$69.90
Purchase #2	$37.57	7.757%	$40.4843	$40.48	$40.50	$40.50
Purchase #3	$48.72	5.744%	$51.5185	$51.52	$51.50	$51.50
Purchase #4	$17.47	13.518%	$19.8316	$19.83	$19.85	$19.80
Purchase #5	$38.31	5.570%	$40.4439	$40.44	$40.45	$40.40
Purchase #6	$181.66	13.238%	$205.7082	$205.71	$205.70	$205.70
Purchase #7	$43.41	3.593%	$44.9697	$44.97	$44.95	$45.00
7 purchase totals =	$430.47		$472.8896	$472.88	$472.90	$472.80