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	$237.97	7.632%	$256.1319	$256.13	$256.15	$256.10
Purchase #2	$204.49	3.634%	$211.9212	$211.92	$211.90	$211.90
Purchase #3	$33.61	9.423%	$36.7771	$36.78	$36.80	$36.80
Purchase #4	$118.88	12.210%	$133.3952	$133.40	$133.40	$133.40
Purchase #5	$134.98	5.779%	$142.7805	$142.78	$142.80	$142.80
Purchase #6	$51.74	7.109%	$55.4182	$55.42	$55.40	$55.40
Purchase #7	$155.43	13.535%	$176.4675	$176.47	$176.45	$176.50
7 purchase totals =	$937.10		$1,012.8916	$1,012.90	$1,012.90	$1,012.90