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	$115.25	5.631%	$121.7397	$121.74	$121.75	$121.70
Purchase #2	$238.30	9.849%	$261.7702	$261.77	$261.75	$261.80
Purchase #3	$90.56	13.127%	$102.4478	$102.45	$102.45	$102.40
Purchase #4	$176.74	12.293%	$198.4666	$198.47	$198.45	$198.50
Purchase #5	$24.31	6.249%	$25.8291	$25.83	$25.85	$25.80
Purchase #6	$96.90	8.873%	$105.4979	$105.50	$105.50	$105.50
Purchase #7	$184.81	10.300%	$203.8454	$203.85	$203.85	$203.80
7 purchase totals =	$926.87		$1,019.5967	$1,019.61	$1,019.60	$1,019.50