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 $195.94   3.196%   $202.2022   $202.20   $202.20   $202.20  
  Purchase #2 $214.80   3.644%   $222.6273   $222.63   $222.65   $222.60  
  Purchase #3 $85.51   5.543%   $90.2498   $90.25   $90.25   $90.20  
  Purchase #4 $99.71   6.851%   $106.5411   $106.54   $106.55   $106.50  
  Purchase #5 $209.99   5.845%   $222.2639   $222.26   $222.25   $222.30  
  Purchase #6 $242.85   9.116%   $264.9882   $264.99   $265.00   $265.00  
  Purchase #7 $56.53   9.475%   $61.8862   $61.89   $61.90   $61.90  
  7 purchase totals = $1,105.33       $1,170.7587   $1,170.76   $1,170.80   $1,170.70