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 $98.93   11.792%   $110.5958   $110.60   $110.60   $110.60  
  Purchase #2 $196.44   10.327%   $216.7264   $216.73   $216.75   $216.70  
  Purchase #3 $227.90   6.257%   $242.1597   $242.16   $242.15   $242.20  
  Purchase #4 $84.68   13.556%   $96.1592   $96.16   $96.15   $96.20  
  Purchase #5 $195.54   9.391%   $213.9032   $213.90   $213.90   $213.90  
  Purchase #6 $186.40   4.652%   $195.0713   $195.07   $195.05   $195.10  
  Purchase #7 $165.50   9.106%   $180.5704   $180.57   $180.55   $180.60  
  7 purchase totals = $1,155.39       $1,255.1860   $1,255.19   $1,255.15   $1,255.30