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 $181.77   8.402%   $197.0423   $197.04   $197.05   $197.00  
  Purchase #2 $150.50   3.620%   $155.9481   $155.95   $155.95   $155.90  
  Purchase #3 $54.83   3.231%   $56.6016   $56.60   $56.60   $56.60  
  Purchase #4 $55.46   12.481%   $62.382   $62.38   $62.40   $62.40  
  Purchase #5 $130.81   6.458%   $139.2577   $139.26   $139.25   $139.30  
  Purchase #6 $188.40   8.841%   $205.0564   $205.06   $205.05   $205.10  
  Purchase #7 $53.99   3.810%   $56.047   $56.05   $56.05   $56.00  
  7 purchase totals = $815.76       $872.3351   $872.34   $872.35   $872.30