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	$13.30	7.762%	$14.3323	$14.33	$14.35	$14.30
Purchase #2	$131.39	9.196%	$143.4726	$143.47	$143.45	$143.50
Purchase #3	$203.27	11.139%	$225.9122	$225.91	$225.90	$225.90
Purchase #4	$55.43	9.223%	$60.5423	$60.54	$60.55	$60.50
Purchase #5	$117.70	12.679%	$132.6232	$132.62	$132.60	$132.60
Purchase #6	$31.70	11.526%	$35.3537	$35.35	$35.35	$35.40
Purchase #7	$89.66	13.132%	$101.4342	$101.43	$101.45	$101.40
7 purchase totals =	$642.45		$713.6705	$713.65	$713.65	$713.60