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	$18.76	11.595%	$20.9352	$20.94	$20.95	$20.90
Purchase #2	$22.80	4.684%	$23.868	$23.87	$23.85	$23.90
Purchase #3	$36.31	10.825%	$40.2406	$40.24	$40.25	$40.20
Purchase #4	$80.80	4.695%	$84.5936	$84.59	$84.60	$84.60
Purchase #5	$118.54	4.203%	$123.5222	$123.52	$123.50	$123.50
Purchase #6	$140.82	5.493%	$148.5552	$148.56	$148.55	$148.60
Purchase #7	$108.37	9.427%	$118.586	$118.59	$118.60	$118.60
7 purchase totals =	$526.40		$560.3008	$560.31	$560.30	$560.30