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	$161.83	6.107%	$171.713	$171.71	$171.70	$171.70
Purchase #2	$207.67	9.352%	$227.0913	$227.09	$227.10	$227.10
Purchase #3	$95.57	8.705%	$103.8894	$103.89	$103.90	$103.90
Purchase #4	$11.29	10.848%	$12.5147	$12.51	$12.50	$12.50
Purchase #5	$77.37	6.456%	$82.365	$82.37	$82.35	$82.40
Purchase #6	$232.97	9.427%	$254.9321	$254.93	$254.95	$254.90
Purchase #7	$158.98	3.396%	$164.379	$164.38	$164.40	$164.40
7 purchase totals =	$945.68		$1,016.8845	$1,016.88	$1,016.90	$1,016.90