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 $237.39   7.827%   $255.9705   $255.97   $255.95   $256.00  
  Purchase #2 $230.62   5.132%   $242.4554   $242.46   $242.45   $242.50  
  Purchase #3 $202.97   5.794%   $214.7301   $214.73   $214.75   $214.70  
  Purchase #4 $238.26   10.301%   $262.8032   $262.80   $262.80   $262.80  
  Purchase #5 $146.70   7.341%   $157.4692   $157.47   $157.45   $157.50  
  Purchase #6 $37.45   4.685%   $39.2045   $39.20   $39.20   $39.20  
  Purchase #7 $20.93   10.852%   $23.2013   $23.20   $23.20   $23.20  
  7 purchase totals = $1,114.32       $1,195.8342   $1,195.83   $1,195.80   $1,195.90