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 $196.69   5.260%   $207.0359   $207.04   $207.05   $207.00  
  Purchase #2 $179.39   4.597%   $187.6366   $187.64   $187.65   $187.60  
  Purchase #3 $205.98   12.633%   $232.0015   $232.00   $232.00   $232.00  
  Purchase #4 $95.77   13.872%   $109.0552   $109.06   $109.05   $109.10  
  Purchase #5 $63.86   5.184%   $67.1705   $67.17   $67.15   $67.20  
  Purchase #6 $236.78   10.845%   $262.4588   $262.46   $262.45   $262.50  
  Purchase #7 $95.83   11.832%   $107.1686   $107.17   $107.15   $107.20  
  7 purchase totals = $1,074.30       $1,172.5271   $1,172.54   $1,172.50   $1,172.60