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	$40.37	7.641%	$43.4547	$43.45	$43.45	$43.50
Purchase #2	$98.38	11.539%	$109.7321	$109.73	$109.75	$109.70
Purchase #3	$79.60	7.421%	$85.5071	$85.51	$85.50	$85.50
Purchase #4	$178.40	7.777%	$192.2742	$192.27	$192.25	$192.30
Purchase #5	$11.32	13.587%	$12.858	$12.86	$12.85	$12.90
Purchase #6	$189.99	8.410%	$205.9682	$205.97	$205.95	$206.00
Purchase #7	$61.72	6.610%	$65.7997	$65.80	$65.80	$65.80
7 purchase totals =	$659.78		$715.5940	$715.59	$715.55	$715.70