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	$91.46	13.655%	$103.9489	$103.95	$103.95	$103.90
Purchase #2	$76.64	6.393%	$81.5396	$81.54	$81.55	$81.50
Purchase #3	$122.63	8.697%	$133.2951	$133.30	$133.30	$133.30
Purchase #4	$226.83	8.641%	$246.4304	$246.43	$246.45	$246.40
Purchase #5	$38.35	10.361%	$42.3234	$42.32	$42.30	$42.30
Purchase #6	$139.63	4.456%	$145.8519	$145.85	$145.85	$145.90
Purchase #7	$237.63	7.554%	$255.5806	$255.58	$255.60	$255.60
7 purchase totals =	$933.17		$1,008.9699	$1,008.97	$1,009.00	$1,008.90