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 $205.75   13.536%   $233.6003   $233.60   $233.60   $233.60  
  Purchase #2 $160.39   10.325%   $176.9503   $176.95   $176.95   $177.00  
  Purchase #3 $134.63   5.404%   $141.9054   $141.91   $141.90   $141.90  
  Purchase #4 $126.91   4.320%   $132.3925   $132.39   $132.40   $132.40  
  Purchase #5 $105.85   11.619%   $118.1487   $118.15   $118.15   $118.10  
  Purchase #6 $48.57   4.598%   $50.8032   $50.80   $50.80   $50.80  
  Purchase #7 $214.99   12.824%   $242.5603   $242.56   $242.55   $242.60  
  7 purchase totals = $997.09       $1,096.3607   $1,096.36   $1,096.35   $1,096.40