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 $195.42   3.702%   $202.6544   $202.65   $202.65   $202.70  
  Purchase #2 $20.64   12.549%   $23.2301   $23.23   $23.25   $23.20  
  Purchase #3 $113.60   9.490%   $124.3806   $124.38   $124.40   $124.40  
  Purchase #4 $151.72   7.308%   $162.8077   $162.81   $162.80   $162.80  
  Purchase #5 $107.63   7.393%   $115.5871   $115.59   $115.60   $115.60  
  Purchase #6 $234.63   8.593%   $254.7918   $254.79   $254.80   $254.80  
  Purchase #7 $58.38   12.274%   $65.5456   $65.55   $65.55   $65.50  
  7 purchase totals = $882.02       $948.9973   $949.00   $949.05   $949.00