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 $93.45   4.402%   $97.5637   $97.56   $97.55   $97.60  
  Purchase #2 $149.73   11.857%   $167.4835   $167.48   $167.50   $167.50  
  Purchase #3 $183.51   13.726%   $208.6986   $208.70   $208.70   $208.70  
  Purchase #4 $171.92   13.187%   $194.5911   $194.59   $194.60   $194.60  
  Purchase #5 $49.86   4.413%   $52.0603   $52.06   $52.05   $52.10  
  Purchase #6 $185.62   11.787%   $207.499   $207.50   $207.50   $207.50  
  Purchase #7 $22.94   13.662%   $26.0741   $26.07   $26.05   $26.10  
  7 purchase totals = $857.03       $953.9703   $953.96   $953.95   $954.10