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 $57.40   8.469%   $62.2612   $62.26   $62.25   $62.30  
  Purchase #2 $250.78   10.234%   $276.4448   $276.44   $276.45   $276.40  
  Purchase #3 $232.48   13.489%   $263.8392   $263.84   $263.85   $263.80  
  Purchase #4 $117.28   11.866%   $131.1964   $131.20   $131.20   $131.20  
  Purchase #5 $174.27   9.246%   $190.383   $190.38   $190.40   $190.40  
  Purchase #6 $114.76   11.871%   $128.3832   $128.38   $128.40   $128.40  
  Purchase #7 $10.76   13.296%   $12.1906   $12.19   $12.20   $12.20  
  7 purchase totals = $957.73       $1,064.6984   $1,064.69   $1,064.75   $1,064.70