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	$99.67	3.609%	$103.2671	$103.27	$103.25	$103.30
Purchase #2	$140.31	12.566%	$157.9414	$157.94	$157.95	$157.90
Purchase #3	$113.28	5.416%	$119.4152	$119.42	$119.40	$119.40
Purchase #4	$160.89	8.533%	$174.6187	$174.62	$174.60	$174.60
Purchase #5	$250.95	13.383%	$284.5346	$284.53	$284.55	$284.50
Purchase #6	$176.40	13.387%	$200.0147	$200.01	$200.00	$200.00
Purchase #7	$34.32	3.742%	$35.6043	$35.60	$35.60	$35.60
7 purchase totals =	$975.82		$1,075.3960	$1,075.39	$1,075.35	$1,075.30