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	$127.36	12.619%	$143.4316	$143.43	$143.45	$143.40
Purchase #2	$47.82	9.546%	$52.3849	$52.38	$52.40	$52.40
Purchase #3	$57.83	4.428%	$60.3907	$60.39	$60.40	$60.40
Purchase #4	$229.35	4.441%	$239.5354	$239.54	$239.55	$239.50
Purchase #5	$215.83	10.462%	$238.4101	$238.41	$238.40	$238.40
Purchase #6	$12.82	12.475%	$14.4193	$14.42	$14.40	$14.40
Purchase #7	$187.51	4.646%	$196.2217	$196.22	$196.20	$196.20
7 purchase totals =	$878.52		$944.7937	$944.79	$944.80	$944.70