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 $113.43   10.784%   $125.6623   $125.66   $125.65   $125.70  
  Purchase #2 $120.39   13.488%   $136.6282   $136.63   $136.65   $136.60  
  Purchase #3 $246.79   12.135%   $276.738   $276.74   $276.75   $276.70  
  Purchase #4 $212.88   11.171%   $236.6608   $236.66   $236.65   $236.70  
  Purchase #5 $234.71   13.498%   $266.3912   $266.39   $266.40   $266.40  
  Purchase #6 $73.80   4.568%   $77.1712   $77.17   $77.15   $77.20  
  Purchase #7 $7.25   8.833%   $7.8904   $7.89   $7.90   $7.90  
  7 purchase totals = $1,009.25       $1,127.1421   $1,127.14   $1,127.15   $1,127.20