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	$184.61	4.260%	$192.4744	$192.47	$192.45	$192.50
Purchase #2	$137.56	4.748%	$144.0913	$144.09	$144.10	$144.10
Purchase #3	$191.37	7.520%	$205.761	$205.76	$205.75	$205.80
Purchase #4	$37.87	7.840%	$40.839	$40.84	$40.85	$40.80
Purchase #5	$46.59	12.724%	$52.5181	$52.52	$52.50	$52.50
Purchase #6	$175.90	6.108%	$186.644	$186.64	$186.65	$186.60
Purchase #7	$225.91	3.870%	$234.6527	$234.65	$234.65	$234.70
7 purchase totals =	$999.81		$1,056.9805	$1,056.97	$1,056.95	$1,057.00