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 $197.25   8.514%   $214.0439   $214.04   $214.05   $214.00  
  Purchase #2 $215.61   10.179%   $237.5569   $237.56   $237.55   $237.60  
  Purchase #3 $126.99   11.446%   $141.5253   $141.53   $141.55   $141.50  
  Purchase #4 $233.92   11.586%   $261.022   $261.02   $261.00   $261.00  
  Purchase #5 $201.44   6.193%   $213.9152   $213.92   $213.90   $213.90  
  Purchase #6 $144.81   11.231%   $161.0736   $161.07   $161.05   $161.10  
  Purchase #7 $41.56   12.115%   $46.595   $46.60   $46.60   $46.60  
  7 purchase totals = $1,161.58       $1,275.7319   $1,275.74   $1,275.70   $1,275.70