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	$225.77	13.702%	$256.705	$256.71	$256.70	$256.70
Purchase #2	$210.55	11.184%	$234.0979	$234.10	$234.10	$234.10
Purchase #3	$222.60	7.166%	$238.5515	$238.55	$238.55	$238.60
Purchase #4	$37.64	12.493%	$42.3424	$42.34	$42.35	$42.30
Purchase #5	$117.44	6.532%	$125.1112	$125.11	$125.10	$125.10
Purchase #6	$105.75	13.534%	$120.0622	$120.06	$120.05	$120.10
Purchase #7	$90.67	10.325%	$100.0317	$100.03	$100.05	$100.00
7 purchase totals =	$1,010.42		$1,116.9019	$1,116.90	$1,116.90	$1,116.90