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	$191.58	4.864%	$200.8985	$200.90	$200.90	$200.90
Purchase #2	$225.89	5.552%	$238.4314	$238.43	$238.45	$238.40
Purchase #3	$214.85	5.755%	$227.2146	$227.21	$227.20	$227.20
Purchase #4	$142.67	12.315%	$160.2398	$160.24	$160.25	$160.20
Purchase #5	$172.91	13.567%	$196.3687	$196.37	$196.35	$196.40
Purchase #6	$118.50	8.462%	$128.5275	$128.53	$128.55	$128.50
Purchase #7	$97.75	6.314%	$103.9219	$103.92	$103.90	$103.90
7 purchase totals =	$1,164.15		$1,255.6024	$1,255.60	$1,255.60	$1,255.50