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	$116.72	9.389%	$127.6788	$127.68	$127.70	$127.70
Purchase #2	$17.30	11.792%	$19.34	$19.34	$19.35	$19.30
Purchase #3	$248.30	9.166%	$271.0592	$271.06	$271.05	$271.10
Purchase #4	$71.92	12.418%	$80.851	$80.85	$80.85	$80.90
Purchase #5	$164.61	10.307%	$181.5764	$181.58	$181.60	$181.60
Purchase #6	$121.33	8.488%	$131.6285	$131.63	$131.65	$131.60
Purchase #7	$207.35	12.847%	$233.9883	$233.99	$234.00	$234.00
7 purchase totals =	$947.53		$1,046.1222	$1,046.13	$1,046.20	$1,046.20