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	$72.85	5.196%	$76.6353	$76.64	$76.65	$76.60
Purchase #2	$228.60	7.258%	$245.1918	$245.19	$245.20	$245.20
Purchase #3	$27.53	4.134%	$28.6681	$28.67	$28.65	$28.70
Purchase #4	$59.41	4.680%	$62.1904	$62.19	$62.20	$62.20
Purchase #5	$213.41	11.726%	$238.4345	$238.43	$238.45	$238.40
Purchase #6	$111.47	10.354%	$123.0116	$123.01	$123.00	$123.00
Purchase #7	$249.32	3.295%	$257.5351	$257.54	$257.55	$257.50
7 purchase totals =	$962.59		$1,031.6668	$1,031.67	$1,031.70	$1,031.60