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 $34.47   5.117%   $36.2338   $36.23   $36.25   $36.20  
  Purchase #2 $247.76   5.545%   $261.4983   $261.50   $261.50   $261.50  
  Purchase #3 $127.79   8.738%   $138.9563   $138.96   $138.95   $139.00  
  Purchase #4 $10.46   12.390%   $11.756   $11.76   $11.75   $11.80  
  Purchase #5 $65.44   8.154%   $70.776   $70.78   $70.80   $70.80  
  Purchase #6 $246.94   3.133%   $254.6766   $254.68   $254.70   $254.70  
  Purchase #7 $229.90   13.294%   $260.4629   $260.46   $260.45   $260.50  
  7 purchase totals = $962.76       $1,034.3599   $1,034.37   $1,034.40   $1,034.50