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	$126.92	12.253%	$142.4715	$142.47	$142.45	$142.50
Purchase #2	$118.60	5.153%	$124.7115	$124.71	$124.70	$124.70
Purchase #3	$39.93	4.405%	$41.6889	$41.69	$41.70	$41.70
Purchase #4	$154.37	6.394%	$164.2404	$164.24	$164.25	$164.20
Purchase #5	$103.29	9.265%	$112.8598	$112.86	$112.85	$112.90
Purchase #6	$119.96	3.756%	$124.4657	$124.47	$124.45	$124.50
Purchase #7	$236.30	13.389%	$267.9382	$267.94	$267.95	$267.90
7 purchase totals =	$899.37		$978.3760	$978.38	$978.35	$978.40