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 $93.43   4.316%   $97.4624   $97.46   $97.45   $97.50  
  Purchase #2 $194.90   12.188%   $218.6544   $218.65   $218.65   $218.70  
  Purchase #3 $118.79   8.273%   $128.6175   $128.62   $128.60   $128.60  
  Purchase #4 $164.83   5.818%   $174.4198   $174.42   $174.40   $174.40  
  Purchase #5 $24.34   5.439%   $25.6639   $25.66   $25.65   $25.70  
  Purchase #6 $77.38   11.215%   $86.0582   $86.06   $86.05   $86.10  
  Purchase #7 $14.79   4.433%   $15.4456   $15.45   $15.45   $15.40  
  7 purchase totals = $688.46       $746.3218   $746.32   $746.25   $746.40