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	$226.38	13.491%	$256.9209	$256.92	$256.90	$256.90
Purchase #2	$162.45	5.285%	$171.0355	$171.04	$171.05	$171.00
Purchase #3	$87.40	7.667%	$94.101	$94.10	$94.10	$94.10
Purchase #4	$119.89	3.371%	$123.9315	$123.93	$123.95	$123.90
Purchase #5	$149.42	12.237%	$167.7045	$167.70	$167.70	$167.70
Purchase #6	$224.71	13.686%	$255.4638	$255.46	$255.45	$255.50
Purchase #7	$198.40	3.559%	$205.4611	$205.46	$205.45	$205.50
7 purchase totals =	$1,168.65		$1,274.6183	$1,274.61	$1,274.60	$1,274.60