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	$56.88	10.429%	$62.812	$62.81	$62.80	$62.80
Purchase #2	$17.59	6.424%	$18.72	$18.72	$18.70	$18.70
Purchase #3	$82.60	4.463%	$86.2864	$86.29	$86.30	$86.30
Purchase #4	$134.39	12.264%	$150.8716	$150.87	$150.85	$150.90
Purchase #5	$62.99	7.621%	$67.7905	$67.79	$67.80	$67.80
Purchase #6	$123.69	6.799%	$132.0997	$132.10	$132.10	$132.10
Purchase #7	$102.66	3.176%	$105.9205	$105.92	$105.90	$105.90
7 purchase totals =	$580.80		$624.5007	$624.50	$624.45	$624.50