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 $114.30   4.328%   $119.2469   $119.25   $119.25   $119.20  
  Purchase #2 $208.76   3.391%   $215.8391   $215.84   $215.85   $215.80  
  Purchase #3 $104.97   5.473%   $110.715   $110.72   $110.70   $110.70  
  Purchase #4 $173.79   13.849%   $197.8582   $197.86   $197.85   $197.90  
  Purchase #5 $161.29   8.732%   $175.3738   $175.37   $175.35   $175.40  
  Purchase #6 $245.38   10.856%   $272.0185   $272.02   $272.00   $272.00  
  Purchase #7 $155.30   12.344%   $174.4702   $174.47   $174.45   $174.50  
  7 purchase totals = $1,163.79       $1,265.5217   $1,265.53   $1,265.45   $1,265.50