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 $68.59   12.155%   $76.9271   $76.93   $76.95   $76.90  
  Purchase #2 $173.74   13.163%   $196.6094   $196.61   $196.60   $196.60  
  Purchase #3 $48.77   13.310%   $55.2613   $55.26   $55.25   $55.30  
  Purchase #4 $89.33   4.725%   $93.5508   $93.55   $93.55   $93.60  
  Purchase #5 $9.54   5.524%   $10.067   $10.07   $10.05   $10.10  
  Purchase #6 $206.61   5.582%   $218.143   $218.14   $218.15   $218.10  
  Purchase #7 $194.84   10.294%   $214.8968   $214.90   $214.90   $214.90  
  7 purchase totals = $791.42       $865.4554   $865.46   $865.45   $865.50