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	$184.80	7.801%	$199.2162	$199.22	$199.20	$199.20
Purchase #2	$38.69	4.299%	$40.3533	$40.35	$40.35	$40.40
Purchase #3	$67.55	7.354%	$72.5176	$72.52	$72.50	$72.50
Purchase #4	$46.33	5.472%	$48.8652	$48.87	$48.85	$48.90
Purchase #5	$35.78	11.850%	$40.0199	$40.02	$40.00	$40.00
Purchase #6	$113.54	7.567%	$122.1316	$122.13	$122.15	$122.10
Purchase #7	$187.81	4.291%	$195.8689	$195.87	$195.85	$195.90
7 purchase totals =	$674.50		$718.9727	$718.98	$718.90	$719.00