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	$220.56	6.795%	$235.5471	$235.55	$235.55	$235.50
Purchase #2	$226.88	8.180%	$245.4388	$245.44	$245.45	$245.40
Purchase #3	$228.35	4.164%	$237.8585	$237.86	$237.85	$237.90
Purchase #4	$153.88	3.262%	$158.8996	$158.90	$158.90	$158.90
Purchase #5	$218.97	10.466%	$241.8874	$241.89	$241.90	$241.90
Purchase #6	$86.54	10.379%	$95.522	$95.52	$95.50	$95.50
Purchase #7	$97.93	8.182%	$105.9426	$105.94	$105.95	$105.90
7 purchase totals =	$1,233.11		$1,321.0960	$1,321.10	$1,321.10	$1,321.00