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 $108.47   5.271%   $114.1875   $114.19   $114.20   $114.20  
  Purchase #2 $198.71   4.651%   $207.952   $207.95   $207.95   $208.00  
  Purchase #3 $128.38   4.814%   $134.5602   $134.56   $134.55   $134.60  
  Purchase #4 $53.68   8.333%   $58.1532   $58.15   $58.15   $58.20  
  Purchase #5 $227.69   11.584%   $254.0656   $254.07   $254.05   $254.10  
  Purchase #6 $74.69   12.460%   $83.9964   $84.00   $84.00   $84.00  
  Purchase #7 $183.86   4.277%   $191.7237   $191.72   $191.70   $191.70  
  7 purchase totals = $975.48       $1,044.6386   $1,044.64   $1,044.60   $1,044.80