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	$111.94	5.500%	$118.0967	$118.10	$118.10	$118.10
Purchase #2	$59.82	5.240%	$62.9546	$62.95	$62.95	$63.00
Purchase #3	$205.45	12.646%	$231.4312	$231.43	$231.45	$231.40
Purchase #4	$209.32	13.767%	$238.1371	$238.14	$238.15	$238.10
Purchase #5	$157.96	5.124%	$166.0539	$166.05	$166.05	$166.10
Purchase #6	$121.99	8.412%	$132.2518	$132.25	$132.25	$132.30
Purchase #7	$206.95	11.854%	$231.4819	$231.48	$231.50	$231.50
7 purchase totals =	$1,073.43		$1,180.4072	$1,180.40	$1,180.45	$1,180.50