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	$52.79	11.770%	$59.0034	$59.00	$59.00	$59.00
Purchase #2	$177.78	8.297%	$192.5304	$192.53	$192.55	$192.50
Purchase #3	$236.81	12.724%	$266.9417	$266.94	$266.95	$266.90
Purchase #4	$158.71	13.583%	$180.2676	$180.27	$180.25	$180.30
Purchase #5	$31.26	10.160%	$34.436	$34.44	$34.45	$34.40
Purchase #6	$177.64	3.834%	$184.4507	$184.45	$184.45	$184.50
Purchase #7	$76.46	3.184%	$78.8945	$78.89	$78.90	$78.90
7 purchase totals =	$911.45		$996.5243	$996.52	$996.55	$996.50