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	$97.67	11.538%	$108.9392	$108.94	$108.95	$108.90
Purchase #2	$198.94	12.265%	$223.34	$223.34	$223.35	$223.30
Purchase #3	$102.62	8.836%	$111.6875	$111.69	$111.70	$111.70
Purchase #4	$39.72	6.731%	$42.3936	$42.39	$42.40	$42.40
Purchase #5	$230.31	11.347%	$256.4433	$256.44	$256.45	$256.40
Purchase #6	$130.38	9.195%	$142.3684	$142.37	$142.35	$142.40
Purchase #7	$158.32	8.626%	$171.9767	$171.98	$172.00	$172.00
7 purchase totals =	$957.96		$1,057.1487	$1,057.15	$1,057.20	$1,057.10