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	$43.91	12.484%	$49.3917	$49.39	$49.40	$49.40
Purchase #2	$29.30	7.365%	$31.4579	$31.46	$31.45	$31.50
Purchase #3	$201.37	12.122%	$225.7801	$225.78	$225.80	$225.80
Purchase #4	$168.38	11.505%	$187.7521	$187.75	$187.75	$187.80
Purchase #5	$13.31	8.755%	$14.4753	$14.48	$14.50	$14.50
Purchase #6	$215.83	3.533%	$223.4553	$223.46	$223.45	$223.50
Purchase #7	$70.86	3.691%	$73.4754	$73.48	$73.50	$73.50
7 purchase totals =	$742.96		$805.7878	$805.80	$805.85	$806.00