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 $25.27   3.814%   $26.2338   $26.23   $26.25   $26.20  
  Purchase #2 $177.39   3.285%   $183.2173   $183.22   $183.20   $183.20  
  Purchase #3 $104.87   5.448%   $110.5833   $110.58   $110.60   $110.60  
  Purchase #4 $246.36   6.840%   $263.211   $263.21   $263.20   $263.20  
  Purchase #5 $178.77   5.357%   $188.3467   $188.35   $188.35   $188.30  
  Purchase #6 $209.25   6.141%   $222.1   $222.10   $222.10   $222.10  
  Purchase #7 $100.71   6.666%   $107.4233   $107.42   $107.40   $107.40  
  7 purchase totals = $1,042.62       $1,101.1154   $1,101.11   $1,101.10   $1,101.00