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 $224.63   10.489%   $248.1914   $248.19   $248.20   $248.20  
  Purchase #2 $249.36   9.438%   $272.8946   $272.89   $272.90   $272.90  
  Purchase #3 $118.63   13.194%   $134.282   $134.28   $134.30   $134.30  
  Purchase #4 $165.39   3.676%   $171.4697   $171.47   $171.45   $171.50  
  Purchase #5 $42.83   4.332%   $44.6854   $44.69   $44.70   $44.70  
  Purchase #6 $132.54   3.701%   $137.4453   $137.45   $137.45   $137.40  
  Purchase #7 $185.68   10.678%   $205.5069   $205.51   $205.50   $205.50  
  7 purchase totals = $1,119.06       $1,214.4753   $1,214.48   $1,214.50   $1,214.50