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	$136.30	6.308%	$144.8978	$144.90	$144.90	$144.90
Purchase #2	$208.46	6.382%	$221.7639	$221.76	$221.75	$221.80
Purchase #3	$12.70	9.863%	$13.9526	$13.95	$13.95	$14.00
Purchase #4	$96.25	3.341%	$99.4657	$99.47	$99.45	$99.50
Purchase #5	$151.94	7.170%	$162.8341	$162.83	$162.85	$162.80
Purchase #6	$132.65	3.845%	$137.7504	$137.75	$137.75	$137.80
Purchase #7	$205.31	13.857%	$233.7598	$233.76	$233.75	$233.80
7 purchase totals =	$943.61		$1,014.4243	$1,014.42	$1,014.40	$1,014.60