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 $56.55   11.847%   $63.2495   $63.25   $63.25   $63.20  
  Purchase #2 $156.66   11.825%   $175.185   $175.19   $175.20   $175.20  
  Purchase #3 $227.27   9.456%   $248.7607   $248.76   $248.75   $248.80  
  Purchase #4 $236.71   10.117%   $260.658   $260.66   $260.65   $260.70  
  Purchase #5 $23.93   9.295%   $26.1543   $26.15   $26.15   $26.20  
  Purchase #6 $245.46   12.737%   $276.7242   $276.72   $276.70   $276.70  
  Purchase #7 $63.86   6.572%   $68.0569   $68.06   $68.05   $68.10  
  7 purchase totals = $1,010.44       $1,118.7886   $1,118.79   $1,118.75   $1,118.90