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	$94.76	9.614%	$103.8702	$103.87	$103.85	$103.90
Purchase #2	$223.59	4.516%	$233.6873	$233.69	$233.70	$233.70
Purchase #3	$116.76	8.853%	$127.0968	$127.10	$127.10	$127.10
Purchase #4	$215.43	3.678%	$223.3535	$223.35	$223.35	$223.40
Purchase #5	$57.89	9.618%	$63.4579	$63.46	$63.45	$63.50
Purchase #6	$109.82	6.826%	$117.3163	$117.32	$117.30	$117.30
Purchase #7	$54.82	6.326%	$58.2879	$58.29	$58.30	$58.30
7 purchase totals =	$873.07		$927.0699	$927.08	$927.05	$927.20