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 $45.81   4.849%   $48.0313   $48.03   $48.05   $48.00  
  Purchase #2 $130.84   8.668%   $142.1812   $142.18   $142.20   $142.20  
  Purchase #3 $242.67   5.795%   $256.7327   $256.73   $256.75   $256.70  
  Purchase #4 $209.77   3.772%   $217.6825   $217.68   $217.70   $217.70  
  Purchase #5 $53.72   6.294%   $57.1011   $57.10   $57.10   $57.10  
  Purchase #6 $58.81   8.818%   $63.9959   $64.00   $64.00   $64.00  
  Purchase #7 $154.58   4.365%   $161.3274   $161.33   $161.35   $161.30  
  7 purchase totals = $896.20       $947.0521   $947.05   $947.15   $947.00