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 $114.45   9.787%   $125.6512   $125.65   $125.65   $125.70  
  Purchase #2 $72.61   8.278%   $78.6207   $78.62   $78.60   $78.60  
  Purchase #3 $205.44   10.755%   $227.5351   $227.54   $227.55   $227.50  
  Purchase #4 $26.61   10.389%   $29.3745   $29.37   $29.35   $29.40  
  Purchase #5 $228.39   7.406%   $245.3046   $245.30   $245.30   $245.30  
  Purchase #6 $103.57   10.140%   $114.072   $114.07   $114.05   $114.10  
  Purchase #7 $162.46   10.582%   $179.6515   $179.65   $179.65   $179.70  
  7 purchase totals = $913.53       $1,000.2096   $1,000.20   $1,000.15   $1,000.30