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 $33.83   4.524%   $35.3605   $35.36   $35.35   $35.40  
  Purchase #2 $114.98   13.572%   $130.5851   $130.59   $130.60   $130.60  
  Purchase #3 $218.42   9.595%   $239.3774   $239.38   $239.40   $239.40  
  Purchase #4 $225.74   11.509%   $251.7204   $251.72   $251.70   $251.70  
  Purchase #5 $199.31   3.386%   $206.0586   $206.06   $206.05   $206.10  
  Purchase #6 $170.95   4.154%   $178.0513   $178.05   $178.05   $178.10  
  Purchase #7 $146.76   11.219%   $163.225   $163.23   $163.25   $163.20  
  7 purchase totals = $1,109.99       $1,204.3783   $1,204.39   $1,204.40   $1,204.50