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	$69.76	4.770%	$73.0876	$73.09	$73.10	$73.10
Purchase #2	$40.84	3.690%	$42.347	$42.35	$42.35	$42.30
Purchase #3	$13.70	5.290%	$14.4247	$14.42	$14.40	$14.40
Purchase #4	$78.86	10.700%	$87.298	$87.30	$87.30	$87.30
Purchase #5	$150.64	10.490%	$166.4421	$166.44	$166.45	$166.40
Purchase #6	$174.83	5.523%	$184.4859	$184.49	$184.50	$184.50
Purchase #7	$13.90	4.451%	$14.5187	$14.52	$14.50	$14.50
7 purchase totals =	$542.53		$582.6040	$582.61	$582.60	$582.50