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	$7.43	6.782%	$7.9339	$7.93	$7.95	$7.90
Purchase #2	$98.35	3.724%	$102.0126	$102.01	$102.00	$102.00
Purchase #3	$41.88	6.667%	$44.6721	$44.67	$44.65	$44.70
Purchase #4	$73.98	6.599%	$78.8619	$78.86	$78.85	$78.90
Purchase #5	$134.48	8.182%	$145.4832	$145.48	$145.50	$145.50
Purchase #6	$78.74	9.589%	$86.2904	$86.29	$86.30	$86.30
Purchase #7	$216.43	10.142%	$238.3803	$238.38	$238.40	$238.40
7 purchase totals =	$651.29		$703.6344	$703.62	$703.65	$703.70