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	$200.64	11.600%	$223.9142	$223.91	$223.90	$223.90
Purchase #2	$71.57	10.212%	$78.8787	$78.88	$78.90	$78.90
Purchase #3	$157.43	7.744%	$169.6214	$169.62	$169.60	$169.60
Purchase #4	$116.72	13.751%	$132.7702	$132.77	$132.75	$132.80
Purchase #5	$47.98	7.218%	$51.4432	$51.44	$51.45	$51.40
Purchase #6	$169.43	3.230%	$174.9026	$174.90	$174.90	$174.90
Purchase #7	$222.50	3.383%	$230.0272	$230.03	$230.05	$230.00
7 purchase totals =	$986.27		$1,061.5575	$1,061.55	$1,061.55	$1,061.50