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 $94.91   10.220%   $104.6098   $104.61   $104.60   $104.60  
  Purchase #2 $195.97   6.864%   $209.4214   $209.42   $209.40   $209.40  
  Purchase #3 $134.97   8.650%   $146.6449   $146.64   $146.65   $146.60  
  Purchase #4 $198.90   6.277%   $211.385   $211.39   $211.40   $211.40  
  Purchase #5 $228.74   5.861%   $242.1465   $242.15   $242.15   $242.10  
  Purchase #6 $78.95   5.626%   $83.3917   $83.39   $83.40   $83.40  
  Purchase #7 $234.26   11.273%   $260.6681   $260.67   $260.65   $260.70  
  7 purchase totals = $1,166.70       $1,258.2674   $1,258.27   $1,258.25   $1,258.20