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	$104.83	12.235%	$117.656	$117.66	$117.65	$117.70
Purchase #2	$54.30	3.595%	$56.2521	$56.25	$56.25	$56.30
Purchase #3	$185.57	7.622%	$199.7141	$199.71	$199.70	$199.70
Purchase #4	$38.46	11.635%	$42.9348	$42.93	$42.95	$42.90
Purchase #5	$168.30	6.401%	$179.0729	$179.07	$179.05	$179.10
Purchase #6	$137.62	4.414%	$143.6945	$143.69	$143.70	$143.70
Purchase #7	$171.54	6.579%	$182.8256	$182.83	$182.85	$182.80
7 purchase totals =	$860.62		$922.1500	$922.14	$922.15	$922.20