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	$237.77	7.765%	$256.2328	$256.23	$256.25	$256.20
Purchase #2	$24.68	13.186%	$27.9343	$27.93	$27.95	$27.90
Purchase #3	$155.53	11.417%	$173.2869	$173.29	$173.30	$173.30
Purchase #4	$84.39	4.343%	$88.0551	$88.06	$88.05	$88.10
Purchase #5	$139.68	11.218%	$155.3493	$155.35	$155.35	$155.30
Purchase #6	$134.70	6.520%	$143.4824	$143.48	$143.50	$143.50
Purchase #7	$156.67	10.473%	$173.078	$173.08	$173.10	$173.10
7 purchase totals =	$933.42		$1,017.4188	$1,017.42	$1,017.50	$1,017.40