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	$145.93	9.705%	$160.0925	$160.09	$160.10	$160.10
Purchase #2	$51.59	5.558%	$54.4574	$54.46	$54.45	$54.50
Purchase #3	$6.52	11.305%	$7.2571	$7.26	$7.25	$7.30
Purchase #4	$233.66	5.480%	$246.4646	$246.46	$246.45	$246.50
Purchase #5	$243.38	4.291%	$253.8234	$253.82	$253.80	$253.80
Purchase #6	$198.96	13.563%	$225.9449	$225.94	$225.95	$225.90
Purchase #7	$159.74	3.158%	$164.7846	$164.78	$164.80	$164.80
7 purchase totals =	$1,039.78		$1,112.8245	$1,112.81	$1,112.80	$1,112.90