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 $49.45   10.530%   $54.6571   $54.66   $54.65   $54.70  
  Purchase #2 $176.81   4.147%   $184.1423   $184.14   $184.15   $184.10  
  Purchase #3 $208.82   6.712%   $222.836   $222.84   $222.85   $222.80  
  Purchase #4 $93.42   8.404%   $101.271   $101.27   $101.25   $101.30  
  Purchase #5 $131.55   6.519%   $140.1257   $140.13   $140.15   $140.10  
  Purchase #6 $217.61   6.659%   $232.1006   $232.10   $232.10   $232.10  
  Purchase #7 $69.70   9.846%   $76.5627   $76.56   $76.55   $76.60  
  7 purchase totals = $947.36       $1,011.6954   $1,011.70   $1,011.70   $1,011.70