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	$216.49	3.746%	$224.5997	$224.60	$224.60	$224.60
Purchase #2	$241.41	6.421%	$256.9109	$256.91	$256.90	$256.90
Purchase #3	$198.60	9.393%	$217.2545	$217.25	$217.25	$217.30
Purchase #4	$90.64	8.616%	$98.4495	$98.45	$98.45	$98.40
Purchase #5	$181.54	4.256%	$189.2663	$189.27	$189.25	$189.30
Purchase #6	$166.76	8.488%	$180.9146	$180.91	$180.90	$180.90
Purchase #7	$208.70	6.648%	$222.5744	$222.57	$222.55	$222.60
7 purchase totals =	$1,304.14		$1,389.9699	$1,389.96	$1,389.90	$1,390.00