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	$51.38	9.126%	$56.0689	$56.07	$56.05	$56.10
Purchase #2	$31.55	6.206%	$33.508	$33.51	$33.50	$33.50
Purchase #3	$11.59	8.260%	$12.5473	$12.55	$12.55	$12.50
Purchase #4	$69.67	11.741%	$77.85	$77.85	$77.85	$77.90
Purchase #5	$66.41	8.436%	$72.0123	$72.01	$72.00	$72.00
Purchase #6	$206.99	6.839%	$221.146	$221.15	$221.15	$221.10
Purchase #7	$241.33	6.280%	$256.4855	$256.49	$256.50	$256.50
7 purchase totals =	$678.92		$729.6180	$729.63	$729.60	$729.60