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	$99.58	12.357%	$111.8851	$111.89	$111.90	$111.90
Purchase #2	$50.67	5.291%	$53.3509	$53.35	$53.35	$53.40
Purchase #3	$20.53	5.724%	$21.7051	$21.71	$21.70	$21.70
Purchase #4	$82.36	3.351%	$85.1199	$85.12	$85.10	$85.10
Purchase #5	$107.26	5.332%	$112.9791	$112.98	$113.00	$113.00
Purchase #6	$84.43	9.734%	$92.6484	$92.65	$92.65	$92.60
Purchase #7	$224.73	7.467%	$241.5106	$241.51	$241.50	$241.50
7 purchase totals =	$669.56		$719.1991	$719.21	$719.20	$719.20