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 $105.57   12.727%   $119.0059   $119.01   $119.00   $119.00  
  Purchase #2 $126.35   7.614%   $135.9703   $135.97   $135.95   $136.00  
  Purchase #3 $196.53   4.670%   $205.708   $205.71   $205.70   $205.70  
  Purchase #4 $132.84   7.542%   $142.8588   $142.86   $142.85   $142.90  
  Purchase #5 $86.75   7.115%   $92.9223   $92.92   $92.90   $92.90  
  Purchase #6 $199.29   4.659%   $208.5749   $208.57   $208.55   $208.60  
  Purchase #7 $180.38   10.803%   $199.8665   $199.87   $199.85   $199.90  
  7 purchase totals = $1,027.71       $1,104.9067   $1,104.91   $1,104.80   $1,105.00