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	$190.70	8.495%	$206.9	$206.90	$206.90	$206.90
Purchase #2	$31.40	3.860%	$32.612	$32.61	$32.60	$32.60
Purchase #3	$47.64	13.231%	$53.9432	$53.94	$53.95	$53.90
Purchase #4	$15.64	12.105%	$17.5332	$17.53	$17.55	$17.50
Purchase #5	$181.63	7.661%	$195.5447	$195.54	$195.55	$195.50
Purchase #6	$111.45	7.873%	$120.2245	$120.22	$120.20	$120.20
Purchase #7	$38.34	4.556%	$40.0868	$40.09	$40.10	$40.10
7 purchase totals =	$616.80		$666.8444	$666.83	$666.85	$666.70