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 $241.41   8.643%   $262.2751   $262.28   $262.30   $262.30  
  Purchase #2 $90.69   7.747%   $97.7158   $97.72   $97.70   $97.70  
  Purchase #3 $94.78   9.281%   $103.5765   $103.58   $103.60   $103.60  
  Purchase #4 $124.35   8.481%   $134.8961   $134.90   $134.90   $134.90  
  Purchase #5 $133.29   6.557%   $142.0298   $142.03   $142.05   $142.00  
  Purchase #6 $124.32   10.708%   $137.6322   $137.63   $137.65   $137.60  
  Purchase #7 $195.96   4.176%   $204.1433   $204.14   $204.15   $204.10  
  7 purchase totals = $1,004.80       $1,082.2688   $1,082.28   $1,082.35   $1,082.20