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 $111.41   12.788%   $125.6571   $125.66   $125.65   $125.70  
  Purchase #2 $206.94   7.371%   $222.1935   $222.19   $222.20   $222.20  
  Purchase #3 $235.80   13.856%   $268.4724   $268.47   $268.45   $268.50  
  Purchase #4 $248.28   10.507%   $274.3668   $274.37   $274.35   $274.40  
  Purchase #5 $8.84   5.429%   $9.3199   $9.32   $9.30   $9.30  
  Purchase #6 $149.43   10.384%   $164.9468   $164.95   $164.95   $164.90  
  Purchase #7 $144.53   11.813%   $161.6033   $161.60   $161.60   $161.60  
  7 purchase totals = $1,105.23       $1,226.5598   $1,226.56   $1,226.50   $1,226.60