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 $185.87   5.268%   $195.6616   $195.66   $195.65   $195.70  
  Purchase #2 $25.87   4.563%   $27.0504   $27.05   $27.05   $27.10  
  Purchase #3 $164.92   4.132%   $171.7345   $171.73   $171.75   $171.70  
  Purchase #4 $159.55   12.586%   $179.631   $179.63   $179.65   $179.60  
  Purchase #5 $140.55   5.599%   $148.4194   $148.42   $148.40   $148.40  
  Purchase #6 $98.99   5.108%   $104.0464   $104.05   $104.05   $104.00  
  Purchase #7 $88.56   12.469%   $99.6025   $99.60   $99.60   $99.60  
  7 purchase totals = $864.31       $926.1458   $926.14   $926.15   $926.10