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 $191.66   5.192%   $201.611   $201.61   $201.60   $201.60  
  Purchase #2 $58.60   4.330%   $61.1374   $61.14   $61.15   $61.10  
  Purchase #3 $190.89   9.776%   $209.5514   $209.55   $209.55   $209.60  
  Purchase #4 $96.38   7.630%   $103.7338   $103.73   $103.75   $103.70  
  Purchase #5 $198.99   3.622%   $206.1974   $206.20   $206.20   $206.20  
  Purchase #6 $11.90   12.814%   $13.4249   $13.42   $13.40   $13.40  
  Purchase #7 $159.50   3.854%   $165.6471   $165.65   $165.65   $165.60  
  7 purchase totals = $907.92       $961.3030   $961.30   $961.30   $961.20