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 $59.65   3.681%   $61.8457   $61.85   $61.85   $61.80  
  Purchase #2 $188.45   3.304%   $194.6764   $194.68   $194.70   $194.70  
  Purchase #3 $102.87   11.515%   $114.7155   $114.72   $114.70   $114.70  
  Purchase #4 $208.55   11.272%   $232.0578   $232.06   $232.05   $232.10  
  Purchase #5 $212.78   5.618%   $224.734   $224.73   $224.75   $224.70  
  Purchase #6 $214.79   12.604%   $241.8621   $241.86   $241.85   $241.90  
  Purchase #7 $187.26   13.845%   $213.1861   $213.19   $213.20   $213.20  
  7 purchase totals = $1,174.35       $1,283.0776   $1,283.09   $1,283.10   $1,283.10