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 $182.71   6.469%   $194.5295   $194.53   $194.55   $194.50  
  Purchase #2 $203.33   8.120%   $219.8404   $219.84   $219.85   $219.80  
  Purchase #3 $71.91   6.105%   $76.3001   $76.30   $76.30   $76.30  
  Purchase #4 $250.76   4.580%   $262.2448   $262.24   $262.25   $262.20  
  Purchase #5 $22.84   7.190%   $24.4822   $24.48   $24.50   $24.50  
  Purchase #6 $105.72   8.497%   $114.703   $114.70   $114.70   $114.70  
  Purchase #7 $188.45   6.516%   $200.7294   $200.73   $200.75   $200.70  
  7 purchase totals = $1,025.72       $1,092.8294   $1,092.82   $1,092.90   $1,092.70