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	$231.37	6.311%	$245.9718	$245.97	$245.95	$246.00
Purchase #2	$151.48	3.147%	$156.2471	$156.25	$156.25	$156.20
Purchase #3	$49.78	8.800%	$54.1606	$54.16	$54.15	$54.20
Purchase #4	$95.59	9.622%	$104.7877	$104.79	$104.80	$104.80
Purchase #5	$149.96	9.679%	$164.4746	$164.47	$164.45	$164.50
Purchase #6	$37.94	3.754%	$39.3643	$39.36	$39.35	$39.40
Purchase #7	$132.77	5.304%	$139.8121	$139.81	$139.80	$139.80
7 purchase totals =	$848.89		$904.8182	$904.81	$904.75	$904.90