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	$239.37	9.127%	$261.2173	$261.22	$261.20	$261.20
Purchase #2	$42.61	5.603%	$44.9974	$45.00	$45.00	$45.00
Purchase #3	$51.75	5.654%	$54.6759	$54.68	$54.70	$54.70
Purchase #4	$54.68	8.812%	$59.4984	$59.50	$59.50	$59.50
Purchase #5	$50.53	11.849%	$56.5173	$56.52	$56.50	$56.50
Purchase #6	$241.75	5.654%	$255.4185	$255.42	$255.40	$255.40
Purchase #7	$94.43	11.223%	$105.0279	$105.03	$105.05	$105.00
7 purchase totals =	$775.12		$837.3527	$837.37	$837.35	$837.30