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	$12.54	12.775%	$14.142	$14.14	$14.15	$14.10
Purchase #2	$99.48	12.546%	$111.9608	$111.96	$111.95	$112.00
Purchase #3	$228.33	4.140%	$237.7829	$237.78	$237.80	$237.80
Purchase #4	$19.37	13.684%	$22.0206	$22.02	$22.00	$22.00
Purchase #5	$36.74	9.564%	$40.2538	$40.25	$40.25	$40.30
Purchase #6	$105.90	5.617%	$111.8484	$111.85	$111.85	$111.80
Purchase #7	$111.33	8.193%	$120.4513	$120.45	$120.45	$120.50
7 purchase totals =	$613.69		$658.4598	$658.45	$658.45	$658.50