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 $208.71   5.161%   $219.4815   $219.48   $219.50   $219.50  
  Purchase #2 $211.68   10.667%   $234.2599   $234.26   $234.25   $234.30  
  Purchase #3 $69.48   13.422%   $78.8056   $78.81   $78.80   $78.80  
  Purchase #4 $65.48   8.715%   $71.1866   $71.19   $71.20   $71.20  
  Purchase #5 $33.77   3.702%   $35.0202   $35.02   $35.00   $35.00  
  Purchase #6 $50.73   11.132%   $56.3773   $56.38   $56.40   $56.40  
  Purchase #7 $234.51   3.376%   $242.4271   $242.43   $242.45   $242.40  
  7 purchase totals = $874.36       $937.5582   $937.57   $937.60   $937.60