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 $160.65   13.374%   $182.1353   $182.14   $182.15   $182.10  
  Purchase #2 $146.55   10.849%   $162.4492   $162.45   $162.45   $162.40  
  Purchase #3 $183.67   13.536%   $208.5316   $208.53   $208.55   $208.50  
  Purchase #4 $58.92   3.382%   $60.9127   $60.91   $60.90   $60.90  
  Purchase #5 $153.81   12.707%   $173.3546   $173.35   $173.35   $173.40  
  Purchase #6 $201.45   13.766%   $229.1816   $229.18   $229.20   $229.20  
  Purchase #7 $46.77   13.657%   $53.1574   $53.16   $53.15   $53.20  
  7 purchase totals = $951.82       $1,069.7224   $1,069.72   $1,069.75   $1,069.70