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 $192.38   5.121%   $202.2318   $202.23   $202.25   $202.20  
  Purchase #2 $164.71   11.264%   $183.2629   $183.26   $183.25   $183.30  
  Purchase #3 $232.59   12.502%   $261.6684   $261.67   $261.65   $261.70  
  Purchase #4 $90.84   3.542%   $94.0576   $94.06   $94.05   $94.10  
  Purchase #5 $62.25   13.656%   $70.7509   $70.75   $70.75   $70.80  
  Purchase #6 $176.59   12.422%   $198.526   $198.53   $198.55   $198.50  
  Purchase #7 $39.58   9.821%   $43.4672   $43.47   $43.45   $43.50  
  7 purchase totals = $958.94       $1,053.9648   $1,053.97   $1,053.95   $1,054.10