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	$10.36	10.825%	$11.4815	$11.48	$11.50	$11.50
Purchase #2	$207.92	4.396%	$217.0602	$217.06	$217.05	$217.10
Purchase #3	$175.31	6.393%	$186.5176	$186.52	$186.50	$186.50
Purchase #4	$133.65	13.622%	$151.8558	$151.86	$151.85	$151.90
Purchase #5	$233.71	6.706%	$249.3826	$249.38	$249.40	$249.40
Purchase #6	$152.83	8.545%	$165.8893	$165.89	$165.90	$165.90
Purchase #7	$143.56	3.523%	$148.6176	$148.62	$148.60	$148.60
7 purchase totals =	$1,057.34		$1,130.8046	$1,130.81	$1,130.80	$1,130.90