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	$188.66	4.161%	$196.5101	$196.51	$196.50	$196.50
Purchase #2	$58.78	12.756%	$66.278	$66.28	$66.30	$66.30
Purchase #3	$248.46	10.227%	$273.87	$273.87	$273.85	$273.90
Purchase #4	$166.30	12.336%	$186.8148	$186.81	$186.80	$186.80
Purchase #5	$19.28	6.149%	$20.4655	$20.47	$20.45	$20.50
Purchase #6	$13.52	7.644%	$14.5535	$14.55	$14.55	$14.60
Purchase #7	$175.47	8.772%	$190.8622	$190.86	$190.85	$190.90
7 purchase totals =	$870.47		$949.3541	$949.35	$949.30	$949.50