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	$192.37	9.345%	$210.347	$210.35	$210.35	$210.30
Purchase #2	$160.39	7.317%	$172.1257	$172.13	$172.15	$172.10
Purchase #3	$49.37	6.717%	$52.6862	$52.69	$52.70	$52.70
Purchase #4	$116.63	5.657%	$123.2278	$123.23	$123.25	$123.20
Purchase #5	$222.49	12.291%	$249.8362	$249.84	$249.85	$249.80
Purchase #6	$108.85	3.672%	$112.847	$112.85	$112.85	$112.80
Purchase #7	$11.33	9.537%	$12.4105	$12.41	$12.40	$12.40
7 purchase totals =	$861.43		$933.4804	$933.50	$933.55	$933.30