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 $115.46   8.722%   $125.5304   $125.53   $125.55   $125.50  
  Purchase #2 $53.58   10.562%   $59.2391   $59.24   $59.25   $59.20  
  Purchase #3 $179.51   9.178%   $195.9854   $195.99   $196.00   $196.00  
  Purchase #4 $164.27   6.302%   $174.6223   $174.62   $174.60   $174.60  
  Purchase #5 $224.25   4.106%   $233.4577   $233.46   $233.45   $233.50  
  Purchase #6 $172.59   10.509%   $190.7275   $190.73   $190.75   $190.70  
  Purchase #7 $201.34   13.167%   $227.8504   $227.85   $227.85   $227.90  
  7 purchase totals = $1,111.00       $1,207.4128   $1,207.42   $1,207.45   $1,207.40