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	$214.47	3.272%	$221.4875	$221.49	$221.50	$221.50
Purchase #2	$76.28	11.167%	$84.7982	$84.80	$84.80	$84.80
Purchase #3	$56.97	7.180%	$61.0604	$61.06	$61.05	$61.10
Purchase #4	$55.50	11.804%	$62.0512	$62.05	$62.05	$62.10
Purchase #5	$246.56	13.396%	$279.5892	$279.59	$279.60	$279.60
Purchase #6	$226.66	10.208%	$249.7975	$249.80	$249.80	$249.80
Purchase #7	$133.90	12.665%	$150.8584	$150.86	$150.85	$150.90
7 purchase totals =	$1,010.34		$1,109.6424	$1,109.65	$1,109.65	$1,109.80