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 $207.62   13.684%   $236.0307   $236.03   $236.05   $236.00  
  Purchase #2 $167.66   13.830%   $190.8474   $190.85   $190.85   $190.80  
  Purchase #3 $214.26   10.697%   $237.1794   $237.18   $237.20   $237.20  
  Purchase #4 $55.97   4.340%   $58.3991   $58.40   $58.40   $58.40  
  Purchase #5 $71.97   6.479%   $76.6329   $76.63   $76.65   $76.60  
  Purchase #6 $157.85   8.443%   $171.1773   $171.18   $171.20   $171.20  
  Purchase #7 $73.64   5.850%   $77.9479   $77.95   $77.95   $77.90  
  7 purchase totals = $948.97       $1,048.2147   $1,048.22   $1,048.30   $1,048.10