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	$86.58	9.187%	$94.5341	$94.53	$94.55	$94.50
Purchase #2	$116.89	5.375%	$123.1728	$123.17	$123.15	$123.20
Purchase #3	$29.37	10.764%	$32.5314	$32.53	$32.55	$32.50
Purchase #4	$104.36	9.258%	$114.0216	$114.02	$114.00	$114.00
Purchase #5	$90.45	11.530%	$100.8789	$100.88	$100.90	$100.90
Purchase #6	$126.27	13.523%	$143.3455	$143.35	$143.35	$143.30
Purchase #7	$122.44	5.437%	$129.0971	$129.10	$129.10	$129.10
7 purchase totals =	$676.36		$737.5814	$737.58	$737.60	$737.50