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 $184.34   8.863%   $200.6781   $200.68   $200.70   $200.70  
  Purchase #2 $59.27   7.728%   $63.8504   $63.85   $63.85   $63.90  
  Purchase #3 $156.53   12.825%   $176.605   $176.61   $176.60   $176.60  
  Purchase #4 $70.29   6.205%   $74.6515   $74.65   $74.65   $74.70  
  Purchase #5 $247.41   5.387%   $260.738   $260.74   $260.75   $260.70  
  Purchase #6 $111.96   6.346%   $119.065   $119.07   $119.05   $119.10  
  Purchase #7 $51.46   9.235%   $56.2123   $56.21   $56.20   $56.20  
  7 purchase totals = $881.26       $951.8003   $951.81   $951.80   $951.90