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 $108.63   9.699%   $119.166   $119.17   $119.15   $119.20  
  Purchase #2 $161.62   8.419%   $175.2268   $175.23   $175.25   $175.20  
  Purchase #3 $42.41   6.685%   $45.2451   $45.25   $45.25   $45.20  
  Purchase #4 $221.38   7.821%   $238.6941   $238.69   $238.70   $238.70  
  Purchase #5 $69.67   3.752%   $72.284   $72.28   $72.30   $72.30  
  Purchase #6 $54.85   6.868%   $58.6171   $58.62   $58.60   $58.60  
  Purchase #7 $193.76   4.292%   $202.0762   $202.08   $202.10   $202.10  
  7 purchase totals = $852.32       $911.3093   $911.32   $911.35   $911.30