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	$100.59	8.241%	$108.8796	$108.88	$108.90	$108.90
Purchase #2	$155.90	8.294%	$168.8303	$168.83	$168.85	$168.80
Purchase #3	$109.45	8.137%	$118.3559	$118.36	$118.35	$118.40
Purchase #4	$114.54	3.568%	$118.6268	$118.63	$118.65	$118.60
Purchase #5	$95.67	10.197%	$105.4255	$105.43	$105.45	$105.40
Purchase #6	$220.27	6.710%	$235.0501	$235.05	$235.05	$235.10
Purchase #7	$214.40	11.725%	$239.5384	$239.54	$239.55	$239.50
7 purchase totals =	$1,010.82		$1,094.7066	$1,094.72	$1,094.80	$1,094.70