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 $97.61   6.690%   $104.1401   $104.14   $104.15   $104.10  
  Purchase #2 $198.34   9.124%   $216.4365   $216.44   $216.45   $216.40  
  Purchase #3 $64.50   8.778%   $70.1618   $70.16   $70.15   $70.20  
  Purchase #4 $22.93   13.416%   $26.0063   $26.01   $26.00   $26.00  
  Purchase #5 $119.59   5.432%   $126.0861   $126.09   $126.10   $126.10  
  Purchase #6 $141.33   8.289%   $153.0448   $153.04   $153.05   $153.00  
  Purchase #7 $56.42   8.448%   $61.1864   $61.19   $61.20   $61.20  
  7 purchase totals = $700.72       $757.0620   $757.07   $757.10   $757.00