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 $55.45   9.524%   $60.7311   $60.73   $60.75   $60.70  
  Purchase #2 $106.50   11.532%   $118.7816   $118.78   $118.80   $118.80  
  Purchase #3 $41.27   8.758%   $44.8844   $44.88   $44.90   $44.90  
  Purchase #4 $161.45   8.836%   $175.7157   $175.72   $175.70   $175.70  
  Purchase #5 $153.25   5.793%   $162.1278   $162.13   $162.15   $162.10  
  Purchase #6 $93.92   9.859%   $103.1796   $103.18   $103.20   $103.20  
  Purchase #7 $87.71   5.760%   $92.7621   $92.76   $92.75   $92.80  
  7 purchase totals = $699.55       $758.1823   $758.18   $758.25   $758.20