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	$149.28	7.838%	$160.9806	$160.98	$161.00	$161.00
Purchase #2	$143.38	13.161%	$162.2502	$162.25	$162.25	$162.30
Purchase #3	$127.72	6.827%	$136.4394	$136.44	$136.45	$136.40
Purchase #4	$200.30	8.665%	$217.656	$217.66	$217.65	$217.70
Purchase #5	$24.68	13.806%	$28.0873	$28.09	$28.10	$28.10
Purchase #6	$133.82	4.310%	$139.5876	$139.59	$139.60	$139.60
Purchase #7	$198.77	8.379%	$215.4249	$215.42	$215.40	$215.40
7 purchase totals =	$977.95		$1,060.4260	$1,060.43	$1,060.45	$1,060.50