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 $88.25   8.256%   $95.5359   $95.54   $95.55   $95.50  
  Purchase #2 $90.71   5.729%   $95.9068   $95.91   $95.90   $95.90  
  Purchase #3 $93.49   4.123%   $97.3446   $97.34   $97.35   $97.30  
  Purchase #4 $232.45   5.132%   $244.3793   $244.38   $244.40   $244.40  
  Purchase #5 $122.80   11.561%   $136.9969   $137.00   $137.00   $137.00  
  Purchase #6 $243.39   7.286%   $261.1234   $261.12   $261.10   $261.10  
  Purchase #7 $32.54   7.787%   $35.0739   $35.07   $35.05   $35.10  
  7 purchase totals = $903.63       $966.3608   $966.36   $966.35   $966.30