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	$223.94	11.240%	$249.1109	$249.11	$249.10	$249.10
Purchase #2	$177.79	10.730%	$196.8669	$196.87	$196.85	$196.90
Purchase #3	$173.39	8.164%	$187.5456	$187.55	$187.55	$187.50
Purchase #4	$183.64	11.824%	$205.3536	$205.35	$205.35	$205.40
Purchase #5	$7.93	12.539%	$8.9243	$8.92	$8.90	$8.90
Purchase #6	$150.67	4.111%	$156.864	$156.86	$156.85	$156.90
Purchase #7	$238.51	5.741%	$252.2029	$252.20	$252.20	$252.20
7 purchase totals =	$1,155.87		$1,256.8682	$1,256.86	$1,256.80	$1,256.90