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	$200.35	3.179%	$206.7191	$206.72	$206.70	$206.70
Purchase #2	$103.89	5.646%	$109.7556	$109.76	$109.75	$109.80
Purchase #3	$124.85	10.358%	$137.782	$137.78	$137.80	$137.80
Purchase #4	$104.94	6.772%	$112.0465	$112.05	$112.05	$112.00
Purchase #5	$181.47	13.756%	$206.433	$206.43	$206.45	$206.40
Purchase #6	$162.37	5.743%	$171.6949	$171.69	$171.70	$171.70
Purchase #7	$112.89	10.317%	$124.5369	$124.54	$124.55	$124.50
7 purchase totals =	$990.76		$1,068.9680	$1,068.97	$1,069.00	$1,068.90