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	$64.36	5.582%	$67.9526	$67.95	$67.95	$68.00
Purchase #2	$86.79	11.564%	$96.8264	$96.83	$96.85	$96.80
Purchase #3	$57.77	6.233%	$61.3708	$61.37	$61.35	$61.40
Purchase #4	$130.85	9.807%	$143.6825	$143.68	$143.70	$143.70
Purchase #5	$97.83	8.152%	$105.8051	$105.81	$105.80	$105.80
Purchase #6	$81.52	10.334%	$89.9443	$89.94	$89.95	$89.90
Purchase #7	$36.67	11.863%	$41.0202	$41.02	$41.00	$41.00
7 purchase totals =	$555.79		$606.6019	$606.60	$606.60	$606.60