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 $47.95   8.816%   $52.1773   $52.18   $52.20   $52.20  
  Purchase #2 $239.85   8.374%   $259.935   $259.94   $259.95   $259.90  
  Purchase #3 $94.93   7.613%   $102.157   $102.16   $102.15   $102.20  
  Purchase #4 $112.43   4.409%   $117.387   $117.39   $117.40   $117.40  
  Purchase #5 $218.48   3.418%   $225.9476   $225.95   $225.95   $225.90  
  Purchase #6 $175.43   10.348%   $193.5835   $193.58   $193.60   $193.60  
  Purchase #7 $244.44   5.547%   $257.9991   $258.00   $258.00   $258.00  
  7 purchase totals = $1,133.51       $1,209.1865   $1,209.20   $1,209.25   $1,209.20