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 $50.49   11.434%   $56.263   $56.26   $56.25   $56.30  
  Purchase #2 $225.36   4.556%   $235.6274   $235.63   $235.65   $235.60  
  Purchase #3 $163.94   12.602%   $184.5997   $184.60   $184.60   $184.60  
  Purchase #4 $143.41   5.353%   $151.0867   $151.09   $151.10   $151.10  
  Purchase #5 $206.73   10.624%   $228.693   $228.69   $228.70   $228.70  
  Purchase #6 $63.29   13.189%   $71.6373   $71.64   $71.65   $71.60  
  Purchase #7 $223.87   13.819%   $254.8066   $254.81   $254.80   $254.80  
  7 purchase totals = $1,077.09       $1,182.7137   $1,182.72   $1,182.75   $1,182.70