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	$114.55	9.546%	$125.4849	$125.48	$125.50	$125.50
Purchase #2	$55.27	3.680%	$57.3039	$57.30	$57.30	$57.30
Purchase #3	$158.94	12.355%	$178.577	$178.58	$178.60	$178.60
Purchase #4	$188.55	5.483%	$198.8882	$198.89	$198.90	$198.90
Purchase #5	$40.60	12.723%	$45.7655	$45.77	$45.75	$45.80
Purchase #6	$192.47	12.190%	$215.9321	$215.93	$215.95	$215.90
Purchase #7	$137.43	4.696%	$143.8837	$143.88	$143.90	$143.90
7 purchase totals =	$887.81		$965.8353	$965.83	$965.90	$965.90