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	$242.33	5.493%	$255.6412	$255.64	$255.65	$255.60
Purchase #2	$47.83	13.124%	$54.1072	$54.11	$54.10	$54.10
Purchase #3	$229.69	12.455%	$258.2979	$258.30	$258.30	$258.30
Purchase #4	$38.29	12.625%	$43.1241	$43.12	$43.10	$43.10
Purchase #5	$67.51	10.309%	$74.4696	$74.47	$74.45	$74.50
Purchase #6	$111.96	11.750%	$125.1153	$125.12	$125.10	$125.10
Purchase #7	$196.29	6.401%	$208.8545	$208.85	$208.85	$208.90
7 purchase totals =	$933.90		$1,019.6098	$1,019.61	$1,019.55	$1,019.60