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	$208.35	9.622%	$228.3974	$228.40	$228.40	$228.40
Purchase #2	$39.63	3.278%	$40.9291	$40.93	$40.95	$40.90
Purchase #3	$153.98	4.158%	$160.3825	$160.38	$160.40	$160.40
Purchase #4	$115.86	6.331%	$123.1951	$123.20	$123.20	$123.20
Purchase #5	$200.89	12.586%	$226.174	$226.17	$226.15	$226.20
Purchase #6	$102.32	10.566%	$113.1311	$113.13	$113.15	$113.10
Purchase #7	$39.32	4.614%	$41.1342	$41.13	$41.15	$41.10
7 purchase totals =	$860.35		$933.3434	$933.34	$933.40	$933.30