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 $195.93   6.773%   $209.2003   $209.20   $209.20   $209.20  
  Purchase #2 $168.77   9.862%   $185.4141   $185.41   $185.40   $185.40  
  Purchase #3 $85.60   13.576%   $97.2211   $97.22   $97.20   $97.20  
  Purchase #4 $243.64   9.796%   $267.507   $267.51   $267.50   $267.50  
  Purchase #5 $103.63   5.393%   $109.2188   $109.22   $109.20   $109.20  
  Purchase #6 $191.74   11.427%   $213.6501   $213.65   $213.65   $213.70  
  Purchase #7 $75.73   6.795%   $80.8759   $80.88   $80.90   $80.90  
  7 purchase totals = $1,065.04       $1,163.0873   $1,163.09   $1,163.05   $1,163.10