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	$217.94	12.650%	$245.5094	$245.51	$245.50	$245.50
Purchase #2	$25.64	13.339%	$29.0601	$29.06	$29.05	$29.10
Purchase #3	$200.94	4.774%	$210.5329	$210.53	$210.55	$210.50
Purchase #4	$89.30	9.376%	$97.6728	$97.67	$97.65	$97.70
Purchase #5	$246.40	13.548%	$279.7823	$279.78	$279.80	$279.80
Purchase #6	$71.96	9.360%	$78.6955	$78.70	$78.70	$78.70
Purchase #7	$66.51	12.392%	$74.7519	$74.75	$74.75	$74.80
7 purchase totals =	$918.69		$1,016.0049	$1,016.00	$1,016.00	$1,016.10