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 $101.81   12.324%   $114.3571   $114.36   $114.35   $114.40  
  Purchase #2 $225.34   12.874%   $254.3503   $254.35   $254.35   $254.40  
  Purchase #3 $107.25   10.677%   $118.7011   $118.70   $118.70   $118.70  
  Purchase #4 $159.43   11.574%   $177.8824   $177.88   $177.90   $177.90  
  Purchase #5 $36.59   13.668%   $41.5911   $41.59   $41.60   $41.60  
  Purchase #6 $138.64   9.458%   $151.7526   $151.75   $151.75   $151.80  
  Purchase #7 $35.25   11.868%   $39.4335   $39.43   $39.45   $39.40  
  7 purchase totals = $804.31       $898.0681   $898.06   $898.10   $898.20