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	$66.88	10.549%	$73.9352	$73.94	$73.95	$73.90
Purchase #2	$33.27	8.384%	$36.0594	$36.06	$36.05	$36.10
Purchase #3	$139.67	13.724%	$158.8383	$158.84	$158.85	$158.80
Purchase #4	$108.72	3.738%	$112.784	$112.78	$112.80	$112.80
Purchase #5	$197.77	12.298%	$222.0918	$222.09	$222.10	$222.10
Purchase #6	$166.59	6.435%	$177.3101	$177.31	$177.30	$177.30
Purchase #7	$227.32	3.457%	$235.1785	$235.18	$235.20	$235.20
7 purchase totals =	$940.22		$1,016.1973	$1,016.20	$1,016.25	$1,016.20