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	$66.45	9.653%	$72.8644	$72.86	$72.85	$72.90
Purchase #2	$44.34	7.397%	$47.6198	$47.62	$47.60	$47.60
Purchase #3	$233.46	7.767%	$251.5928	$251.59	$251.60	$251.60
Purchase #4	$42.50	11.455%	$47.3684	$47.37	$47.35	$47.40
Purchase #5	$221.74	7.555%	$238.4925	$238.49	$238.50	$238.50
Purchase #6	$239.57	7.502%	$257.5425	$257.54	$257.55	$257.50
Purchase #7	$113.89	5.863%	$120.5674	$120.57	$120.55	$120.60
7 purchase totals =	$961.95		$1,036.0478	$1,036.04	$1,036.00	$1,036.10