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	$108.40	8.861%	$118.0053	$118.01	$118.00	$118.00
Purchase #2	$142.55	7.748%	$153.5948	$153.59	$153.60	$153.60
Purchase #3	$190.72	9.307%	$208.4703	$208.47	$208.45	$208.50
Purchase #4	$204.87	3.645%	$212.3375	$212.34	$212.35	$212.30
Purchase #5	$95.36	13.848%	$108.5655	$108.57	$108.55	$108.60
Purchase #6	$244.34	10.338%	$269.5999	$269.60	$269.60	$269.60
Purchase #7	$78.98	4.470%	$82.5104	$82.51	$82.50	$82.50
7 purchase totals =	$1,065.22		$1,153.0837	$1,153.09	$1,153.05	$1,153.10