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 $189.96   8.269%   $205.6678   $205.67   $205.65   $205.70  
  Purchase #2 $116.76   12.542%   $131.404   $131.40   $131.40   $131.40  
  Purchase #3 $56.69   11.183%   $63.0296   $63.03   $63.05   $63.00  
  Purchase #4 $143.47   13.578%   $162.9504   $162.95   $162.95   $163.00  
  Purchase #5 $239.96   4.439%   $250.6118   $250.61   $250.60   $250.60  
  Purchase #6 $124.92   10.652%   $138.2265   $138.23   $138.25   $138.20  
  Purchase #7 $97.28   13.246%   $110.1657   $110.17   $110.15   $110.20  
  7 purchase totals = $969.04       $1,062.0558   $1,062.06   $1,062.05   $1,062.10