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 $190.29   5.289%   $200.3544   $200.35   $200.35   $200.40  
  Purchase #2 $59.68   3.391%   $61.7037   $61.70   $61.70   $61.70  
  Purchase #3 $244.42   6.326%   $259.882   $259.88   $259.90   $259.90  
  Purchase #4 $187.29   12.338%   $210.3978   $210.40   $210.40   $210.40  
  Purchase #5 $185.96   6.257%   $197.5955   $197.60   $197.60   $197.60  
  Purchase #6 $76.59   4.189%   $79.7984   $79.80   $79.80   $79.80  
  Purchase #7 $98.73   6.278%   $104.9283   $104.93   $104.95   $104.90  
  7 purchase totals = $1,042.96       $1,114.6601   $1,114.66   $1,114.70   $1,114.70