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 $229.95   6.780%   $245.5406   $245.54   $245.55   $245.50  
  Purchase #2 $95.28   9.178%   $104.0248   $104.02   $104.00   $104.00  
  Purchase #3 $202.31   10.858%   $224.2768   $224.28   $224.30   $224.30  
  Purchase #4 $66.70   10.143%   $73.4654   $73.47   $73.45   $73.50  
  Purchase #5 $41.94   13.480%   $47.5935   $47.59   $47.60   $47.60  
  Purchase #6 $179.56   10.666%   $198.7119   $198.71   $198.70   $198.70  
  Purchase #7 $192.81   11.141%   $214.291   $214.29   $214.30   $214.30  
  7 purchase totals = $1,008.55       $1,107.9040   $1,107.90   $1,107.90   $1,107.90