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	$208.55	12.164%	$233.918	$233.92	$233.90	$233.90
Purchase #2	$77.81	3.439%	$80.4859	$80.49	$80.50	$80.50
Purchase #3	$153.79	7.147%	$164.7814	$164.78	$164.80	$164.80
Purchase #4	$118.93	11.535%	$132.6486	$132.65	$132.65	$132.60
Purchase #5	$97.30	8.871%	$105.9315	$105.93	$105.95	$105.90
Purchase #6	$246.45	4.814%	$258.3141	$258.31	$258.30	$258.30
Purchase #7	$82.83	7.527%	$89.0646	$89.06	$89.05	$89.10
7 purchase totals =	$985.66		$1,065.1441	$1,065.14	$1,065.15	$1,065.10