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	$118.31	4.350%	$123.4565	$123.46	$123.45	$123.50
Purchase #2	$40.42	10.302%	$44.5841	$44.58	$44.60	$44.60
Purchase #3	$228.75	12.311%	$256.9114	$256.91	$256.90	$256.90
Purchase #4	$105.34	13.225%	$119.2712	$119.27	$119.25	$119.30
Purchase #5	$113.72	3.681%	$117.906	$117.91	$117.90	$117.90
Purchase #6	$65.96	7.257%	$70.7467	$70.75	$70.75	$70.70
Purchase #7	$233.77	12.225%	$262.3484	$262.35	$262.35	$262.30
7 purchase totals =	$906.27		$995.2243	$995.23	$995.20	$995.20