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	$132.46	9.522%	$145.0728	$145.07	$145.05	$145.10
Purchase #2	$196.56	7.263%	$210.8362	$210.84	$210.85	$210.80
Purchase #3	$39.32	6.464%	$41.8616	$41.86	$41.85	$41.90
Purchase #4	$131.86	9.553%	$144.4566	$144.46	$144.45	$144.50
Purchase #5	$127.68	4.180%	$133.017	$133.02	$133.00	$133.00
Purchase #6	$72.50	7.723%	$78.0992	$78.10	$78.10	$78.10
Purchase #7	$86.77	10.781%	$96.1247	$96.12	$96.10	$96.10
7 purchase totals =	$787.15		$849.4681	$849.47	$849.40	$849.50