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	$76.30	12.535%	$85.8642	$85.86	$85.85	$85.90
Purchase #2	$81.97	12.211%	$91.9794	$91.98	$92.00	$92.00
Purchase #3	$86.82	4.754%	$90.9474	$90.95	$90.95	$90.90
Purchase #4	$31.85	13.211%	$36.0577	$36.06	$36.05	$36.10
Purchase #5	$102.76	13.764%	$116.9039	$116.90	$116.90	$116.90
Purchase #6	$231.61	5.789%	$245.0179	$245.02	$245.00	$245.00
Purchase #7	$180.43	5.150%	$189.7221	$189.72	$189.70	$189.70
7 purchase totals =	$791.74		$856.4926	$856.49	$856.45	$856.50