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	$179.95	8.269%	$194.8301	$194.83	$194.85	$194.80
Purchase #2	$192.56	9.509%	$210.8705	$210.87	$210.85	$210.90
Purchase #3	$246.80	11.374%	$274.871	$274.87	$274.85	$274.90
Purchase #4	$108.32	10.393%	$119.5777	$119.58	$119.60	$119.60
Purchase #5	$72.54	7.808%	$78.2039	$78.20	$78.20	$78.20
Purchase #6	$249.35	12.784%	$281.2269	$281.23	$281.25	$281.20
Purchase #7	$179.90	9.370%	$196.7566	$196.76	$196.75	$196.80
7 purchase totals =	$1,229.42		$1,356.3367	$1,356.34	$1,356.35	$1,356.40