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	$37.96	8.508%	$41.1896	$41.19	$41.20	$41.20
Purchase #2	$75.56	3.724%	$78.3739	$78.37	$78.35	$78.40
Purchase #3	$98.35	10.207%	$108.3886	$108.39	$108.40	$108.40
Purchase #4	$227.31	12.437%	$255.5805	$255.58	$255.60	$255.60
Purchase #5	$176.87	10.711%	$195.8145	$195.81	$195.80	$195.80
Purchase #6	$214.46	12.522%	$241.3147	$241.31	$241.30	$241.30
Purchase #7	$173.66	9.690%	$190.4877	$190.49	$190.50	$190.50
7 purchase totals =	$1,004.17		$1,111.1495	$1,111.14	$1,111.15	$1,111.20