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	$192.29	9.645%	$210.8364	$210.84	$210.85	$210.80
Purchase #2	$62.96	4.705%	$65.9223	$65.92	$65.90	$65.90
Purchase #3	$80.62	12.226%	$90.4766	$90.48	$90.50	$90.50
Purchase #4	$118.85	4.678%	$124.4098	$124.41	$124.40	$124.40
Purchase #5	$46.67	4.767%	$48.8948	$48.89	$48.90	$48.90
Purchase #6	$132.65	3.174%	$136.8603	$136.86	$136.85	$136.90
Purchase #7	$228.85	4.455%	$239.0453	$239.05	$239.05	$239.00
7 purchase totals =	$862.89		$916.4455	$916.45	$916.45	$916.40