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 $86.51   9.869%   $95.0477   $95.05   $95.05   $95.00  
  Purchase #2 $96.77   4.133%   $100.7695   $100.77   $100.75   $100.80  
  Purchase #3 $88.78   9.273%   $97.0126   $97.01   $97.00   $97.00  
  Purchase #4 $222.79   7.437%   $239.3589   $239.36   $239.35   $239.40  
  Purchase #5 $88.97   8.583%   $96.6063   $96.61   $96.60   $96.60  
  Purchase #6 $158.98   3.734%   $164.9163   $164.92   $164.90   $164.90  
  Purchase #7 $69.57   3.324%   $71.8825   $71.88   $71.90   $71.90  
  7 purchase totals = $812.37       $865.5938   $865.60   $865.55   $865.60