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 $124.94   5.850%   $132.249   $132.25   $132.25   $132.20  
  Purchase #2 $206.90   3.145%   $213.407   $213.41   $213.40   $213.40  
  Purchase #3 $156.29   13.207%   $176.9312   $176.93   $176.95   $176.90  
  Purchase #4 $8.77   7.266%   $9.4072   $9.41   $9.40   $9.40  
  Purchase #5 $177.62   5.207%   $186.8687   $186.87   $186.85   $186.90  
  Purchase #6 $175.63   4.563%   $183.644   $183.64   $183.65   $183.60  
  Purchase #7 $185.70   12.346%   $208.6265   $208.63   $208.65   $208.60  
  7 purchase totals = $1,035.85       $1,111.1336   $1,111.14   $1,111.15   $1,111.00