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	$200.70	8.334%	$217.4263	$217.43	$217.45	$217.40
Purchase #2	$5.74	11.791%	$6.4168	$6.42	$6.40	$6.40
Purchase #3	$76.46	11.693%	$85.4005	$85.40	$85.40	$85.40
Purchase #4	$25.46	9.620%	$27.9093	$27.91	$27.90	$27.90
Purchase #5	$110.64	7.625%	$119.0763	$119.08	$119.10	$119.10
Purchase #6	$137.58	4.867%	$144.276	$144.28	$144.30	$144.30
Purchase #7	$213.95	3.794%	$222.0673	$222.07	$222.05	$222.10
7 purchase totals =	$770.53		$822.5725	$822.59	$822.60	$822.60