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 $185.64   9.693%   $203.6341   $203.63   $203.65   $203.60  
  Purchase #2 $222.95   10.382%   $246.0967   $246.10   $246.10   $246.10  
  Purchase #3 $225.42   11.243%   $250.764   $250.76   $250.75   $250.80  
  Purchase #4 $5.58   8.549%   $6.057   $6.06   $6.05   $6.10  
  Purchase #5 $75.41   12.617%   $84.9245   $84.92   $84.90   $84.90  
  Purchase #6 $163.89   3.334%   $169.3541   $169.35   $169.35   $169.40  
  Purchase #7 $174.49   5.544%   $184.1637   $184.16   $184.15   $184.20  
  7 purchase totals = $1,053.38       $1,144.9941   $1,144.98   $1,144.95   $1,145.10