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 $179.39   9.604%   $196.6186   $196.62   $196.60   $196.60  
  Purchase #2 $241.75   8.360%   $261.9603   $261.96   $261.95   $262.00  
  Purchase #3 $241.84   13.805%   $275.226   $275.23   $275.25   $275.20  
  Purchase #4 $92.93   5.325%   $97.8785   $97.88   $97.90   $97.90  
  Purchase #5 $82.40   10.440%   $91.0026   $91.00   $91.00   $91.00  
  Purchase #6 $69.33   8.782%   $75.4186   $75.42   $75.40   $75.40  
  Purchase #7 $103.61   6.486%   $110.3301   $110.33   $110.35   $110.30  
  7 purchase totals = $1,011.25       $1,108.4347   $1,108.44   $1,108.45   $1,108.40