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	$209.45	7.691%	$225.5588	$225.56	$225.55	$225.60
Purchase #2	$41.41	5.640%	$43.7455	$43.75	$43.75	$43.70
Purchase #3	$234.89	4.676%	$245.8735	$245.87	$245.85	$245.90
Purchase #4	$24.77	12.188%	$27.789	$27.79	$27.80	$27.80
Purchase #5	$103.45	12.504%	$116.3854	$116.39	$116.40	$116.40
Purchase #6	$72.46	13.182%	$82.0117	$82.01	$82.00	$82.00
Purchase #7	$12.62	7.523%	$13.5694	$13.57	$13.55	$13.60
7 purchase totals =	$699.05		$754.9333	$754.94	$754.90	$755.00