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 $118.70   5.867%   $125.6641   $125.66   $125.65   $125.70  
  Purchase #2 $166.71   8.377%   $180.6753   $180.68   $180.70   $180.70  
  Purchase #3 $133.89   9.262%   $146.2909   $146.29   $146.30   $146.30  
  Purchase #4 $223.42   8.652%   $242.7503   $242.75   $242.75   $242.80  
  Purchase #5 $85.69   7.215%   $91.8725   $91.87   $91.85   $91.90  
  Purchase #6 $119.68   13.299%   $135.5962   $135.60   $135.60   $135.60  
  Purchase #7 $30.70   6.385%   $32.6602   $32.66   $32.65   $32.70  
  7 purchase totals = $878.79       $955.5095   $955.51   $955.50   $955.70