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 $191.71   3.617%   $198.6442   $198.64   $198.65   $198.60  
  Purchase #2 $104.62   10.823%   $115.943   $115.94   $115.95   $115.90  
  Purchase #3 $94.91   7.767%   $102.2817   $102.28   $102.30   $102.30  
  Purchase #4 $193.90   4.302%   $202.2416   $202.24   $202.25   $202.20  
  Purchase #5 $236.69   10.151%   $260.7164   $260.72   $260.70   $260.70  
  Purchase #6 $180.47   8.186%   $195.2433   $195.24   $195.25   $195.20  
  Purchase #7 $42.29   6.106%   $44.8722   $44.87   $44.85   $44.90  
  7 purchase totals = $1,044.59       $1,119.9424   $1,119.93   $1,119.95   $1,119.80