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 $73.67   4.815%   $77.2172   $77.22   $77.20   $77.20  
  Purchase #2 $231.86   3.373%   $239.6806   $239.68   $239.70   $239.70  
  Purchase #3 $59.48   7.411%   $63.8881   $63.89   $63.90   $63.90  
  Purchase #4 $209.40   5.265%   $220.4249   $220.42   $220.40   $220.40  
  Purchase #5 $245.97   8.201%   $266.142   $266.14   $266.15   $266.10  
  Purchase #6 $72.65   4.808%   $76.143   $76.14   $76.15   $76.10  
  Purchase #7 $162.31   4.225%   $169.1676   $169.17   $169.15   $169.20  
  7 purchase totals = $1,055.34       $1,112.6634   $1,112.66   $1,112.65   $1,112.60