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 $222.66   9.602%   $244.0398   $244.04   $244.05   $244.00  
  Purchase #2 $235.99   9.828%   $259.1831   $259.18   $259.20   $259.20  
  Purchase #3 $93.68   11.599%   $104.5459   $104.55   $104.55   $104.50  
  Purchase #4 $168.64   9.442%   $184.563   $184.56   $184.55   $184.60  
  Purchase #5 $5.31   4.489%   $5.5484   $5.55   $5.55   $5.50  
  Purchase #6 $199.86   8.364%   $216.5763   $216.58   $216.60   $216.60  
  Purchase #7 $34.86   10.368%   $38.4743   $38.47   $38.45   $38.50  
  7 purchase totals = $961.00       $1,052.9308   $1,052.93   $1,052.95   $1,052.90