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 $195.84   4.805%   $205.2501   $205.25   $205.25   $205.30  
  Purchase #2 $69.41   10.477%   $76.6821   $76.68   $76.70   $76.70  
  Purchase #3 $183.58   12.772%   $207.0268   $207.03   $207.05   $207.00  
  Purchase #4 $157.87   10.565%   $174.549   $174.55   $174.55   $174.50  
  Purchase #5 $209.25   12.841%   $236.1198   $236.12   $236.10   $236.10  
  Purchase #6 $231.58   4.835%   $242.7769   $242.78   $242.80   $242.80  
  Purchase #7 $234.91   7.306%   $252.0725   $252.07   $252.05   $252.10  
  7 purchase totals = $1,282.44       $1,394.4772   $1,394.48   $1,394.50   $1,394.50