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 $119.28   5.782%   $126.1768   $126.18   $126.20   $126.20  
  Purchase #2 $97.58   13.321%   $110.5786   $110.58   $110.60   $110.60  
  Purchase #3 $166.68   12.841%   $188.0834   $188.08   $188.10   $188.10  
  Purchase #4 $136.90   6.649%   $146.0025   $146.00   $146.00   $146.00  
  Purchase #5 $207.63   9.334%   $227.0102   $227.01   $227.00   $227.00  
  Purchase #6 $24.39   6.554%   $25.9885   $25.99   $26.00   $26.00  
  Purchase #7 $250.40   5.340%   $263.7714   $263.77   $263.75   $263.80  
  7 purchase totals = $1,002.86       $1,087.6114   $1,087.61   $1,087.65   $1,087.70