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 $186.81   5.239%   $196.597   $196.60   $196.60   $196.60  
  Purchase #2 $212.87   6.713%   $227.16   $227.16   $227.15   $227.20  
  Purchase #3 $57.82   6.739%   $61.7165   $61.72   $61.70   $61.70  
  Purchase #4 $80.51   9.144%   $87.8718   $87.87   $87.85   $87.90  
  Purchase #5 $90.67   12.787%   $102.264   $102.26   $102.25   $102.30  
  Purchase #6 $20.73   13.338%   $23.495   $23.50   $23.50   $23.50  
  Purchase #7 $246.65   3.146%   $254.4096   $254.41   $254.40   $254.40  
  7 purchase totals = $896.06       $953.5139   $953.52   $953.45   $953.60