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 $173.50   13.560%   $197.0266   $197.03   $197.05   $197.00  
  Purchase #2 $31.42   11.451%   $35.0179   $35.02   $35.00   $35.00  
  Purchase #3 $114.92   7.562%   $123.6103   $123.61   $123.60   $123.60  
  Purchase #4 $185.59   11.847%   $207.5768   $207.58   $207.60   $207.60  
  Purchase #5 $123.97   6.682%   $132.2537   $132.25   $132.25   $132.30  
  Purchase #6 $238.74   3.520%   $247.1436   $247.14   $247.15   $247.10  
  Purchase #7 $239.60   9.370%   $262.0505   $262.05   $262.05   $262.10  
  7 purchase totals = $1,107.74       $1,204.6794   $1,204.68   $1,204.70   $1,204.70