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 $156.79   4.350%   $163.6104   $163.61   $163.60   $163.60  
  Purchase #2 $170.50   12.358%   $191.5704   $191.57   $191.55   $191.60  
  Purchase #3 $182.66   10.463%   $201.7717   $201.77   $201.75   $201.80  
  Purchase #4 $25.69   3.652%   $26.6282   $26.63   $26.65   $26.60  
  Purchase #5 $160.31   3.341%   $165.666   $165.67   $165.65   $165.70  
  Purchase #6 $222.51   12.690%   $250.7465   $250.75   $250.75   $250.70  
  Purchase #7 $115.81   8.457%   $125.6041   $125.60   $125.60   $125.60  
  7 purchase totals = $1,034.27       $1,125.5973   $1,125.60   $1,125.55   $1,125.60