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 $117.30   6.713%   $125.1743   $125.17   $125.15   $125.20  
  Purchase #2 $66.72   5.141%   $70.1501   $70.15   $70.15   $70.20  
  Purchase #3 $169.32   3.868%   $175.8693   $175.87   $175.85   $175.90  
  Purchase #4 $191.70   3.604%   $198.6089   $198.61   $198.60   $198.60  
  Purchase #5 $70.26   5.523%   $74.1405   $74.14   $74.15   $74.10  
  Purchase #6 $120.34   13.197%   $136.2213   $136.22   $136.20   $136.20  
  Purchase #7 $217.99   11.111%   $242.2109   $242.21   $242.20   $242.20  
  7 purchase totals = $953.63       $1,022.3753   $1,022.37   $1,022.30   $1,022.40