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 $173.62   11.449%   $193.4978   $193.50   $193.50   $193.50  
  Purchase #2 $158.38   11.252%   $176.2009   $176.20   $176.20   $176.20  
  Purchase #3 $105.64   10.863%   $117.1157   $117.12   $117.10   $117.10  
  Purchase #4 $72.48   12.771%   $81.7364   $81.74   $81.75   $81.70  
  Purchase #5 $67.83   8.595%   $73.66   $73.66   $73.65   $73.70  
  Purchase #6 $220.62   6.774%   $235.5648   $235.56   $235.55   $235.60  
  Purchase #7 $71.25   6.227%   $75.6867   $75.69   $75.70   $75.70  
  7 purchase totals = $869.82       $953.4623   $953.47   $953.45   $953.50