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 $95.88   9.230%   $104.7297   $104.73   $104.75   $104.70  
  Purchase #2 $239.65   11.682%   $267.6459   $267.65   $267.65   $267.60  
  Purchase #3 $69.81   9.585%   $76.5013   $76.50   $76.50   $76.50  
  Purchase #4 $104.72   9.106%   $114.2558   $114.26   $114.25   $114.30  
  Purchase #5 $213.59   7.193%   $228.9535   $228.95   $228.95   $229.00  
  Purchase #6 $201.67   7.452%   $216.6984   $216.70   $216.70   $216.70  
  Purchase #7 $130.35   9.541%   $142.7867   $142.79   $142.80   $142.80  
  7 purchase totals = $1,055.67       $1,151.5713   $1,151.58   $1,151.60   $1,151.60