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	$246.63	13.783%	$280.623	$280.62	$280.60	$280.60
Purchase #2	$169.62	13.504%	$192.5255	$192.53	$192.55	$192.50
Purchase #3	$141.85	8.703%	$154.1952	$154.20	$154.20	$154.20
Purchase #4	$69.56	12.521%	$78.2696	$78.27	$78.25	$78.30
Purchase #5	$68.27	11.411%	$76.0603	$76.06	$76.05	$76.10
Purchase #6	$9.86	4.189%	$10.273	$10.27	$10.25	$10.30
Purchase #7	$240.64	3.609%	$249.3247	$249.32	$249.30	$249.30
7 purchase totals =	$946.43		$1,041.2713	$1,041.27	$1,041.20	$1,041.30