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	$176.34	6.833%	$188.3893	$188.39	$188.40	$188.40
Purchase #2	$34.46	8.593%	$37.4211	$37.42	$37.40	$37.40
Purchase #3	$112.47	13.604%	$127.7704	$127.77	$127.75	$127.80
Purchase #4	$181.26	6.631%	$193.2794	$193.28	$193.30	$193.30
Purchase #5	$147.43	13.838%	$167.8314	$167.83	$167.85	$167.80
Purchase #6	$202.43	5.747%	$214.0637	$214.06	$214.05	$214.10
Purchase #7	$66.65	8.295%	$72.1786	$72.18	$72.20	$72.20
7 purchase totals =	$921.04		$1,000.9339	$1,000.93	$1,000.95	$1,001.00