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 $33.36   6.301%   $35.462   $35.46   $35.45   $35.50  
  Purchase #2 $142.42   3.554%   $147.4816   $147.48   $147.50   $147.50  
  Purchase #3 $27.67   4.709%   $28.973   $28.97   $28.95   $29.00  
  Purchase #4 $49.66   6.582%   $52.9286   $52.93   $52.95   $52.90  
  Purchase #5 $239.27   9.437%   $261.8499   $261.85   $261.85   $261.80  
  Purchase #6 $234.67   10.714%   $259.8125   $259.81   $259.80   $259.80  
  Purchase #7 $154.42   7.229%   $165.583   $165.58   $165.60   $165.60  
  7 purchase totals = $881.47       $952.0906   $952.08   $952.10   $952.10