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	$199.97	11.751%	$223.4685	$223.47	$223.45	$223.50
Purchase #2	$51.36	9.777%	$56.3815	$56.38	$56.40	$56.40
Purchase #3	$229.25	11.783%	$256.2625	$256.26	$256.25	$256.30
Purchase #4	$201.83	10.184%	$222.3844	$222.38	$222.40	$222.40
Purchase #5	$88.54	10.606%	$97.9306	$97.93	$97.95	$97.90
Purchase #6	$136.97	13.172%	$155.0117	$155.01	$155.00	$155.00
Purchase #7	$123.93	7.523%	$133.2533	$133.25	$133.25	$133.30
7 purchase totals =	$1,031.85		$1,144.6925	$1,144.68	$1,144.70	$1,144.80