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	$41.41	6.582%	$44.1356	$44.14	$44.15	$44.10
Purchase #2	$198.61	10.259%	$218.9854	$218.99	$219.00	$219.00
Purchase #3	$26.67	4.570%	$27.8888	$27.89	$27.90	$27.90
Purchase #4	$166.38	3.622%	$172.4063	$172.41	$172.40	$172.40
Purchase #5	$46.88	9.854%	$51.4996	$51.50	$51.50	$51.50
Purchase #6	$40.87	5.293%	$43.0332	$43.03	$43.05	$43.00
Purchase #7	$47.50	10.466%	$52.4714	$52.47	$52.45	$52.50
7 purchase totals =	$568.32		$610.4203	$610.43	$610.45	$610.40