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 $209.66   11.188%   $233.1168   $233.12   $233.10   $233.10  
  Purchase #2 $21.46   9.235%   $23.4418   $23.44   $23.45   $23.40  
  Purchase #3 $104.33   13.112%   $118.0097   $118.01   $118.00   $118.00  
  Purchase #4 $72.95   3.102%   $75.2129   $75.21   $75.20   $75.20  
  Purchase #5 $182.93   13.719%   $208.0262   $208.03   $208.05   $208.00  
  Purchase #6 $193.75   10.575%   $214.2391   $214.24   $214.25   $214.20  
  Purchase #7 $245.37   5.571%   $259.0396   $259.04   $259.05   $259.00  
  7 purchase totals = $1,030.45       $1,131.0861   $1,131.09   $1,131.10   $1,130.90