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 $73.56   4.166%   $76.6245   $76.62   $76.60   $76.60  
  Purchase #2 $229.35   10.704%   $253.8996   $253.90   $253.90   $253.90  
  Purchase #3 $162.95   6.863%   $174.1333   $174.13   $174.15   $174.10  
  Purchase #4 $42.97   4.306%   $44.8203   $44.82   $44.80   $44.80  
  Purchase #5 $176.27   6.867%   $188.3745   $188.37   $188.35   $188.40  
  Purchase #6 $166.77   7.829%   $179.8264   $179.83   $179.85   $179.80  
  Purchase #7 $122.69   3.361%   $126.8136   $126.81   $126.80   $126.80  
  7 purchase totals = $974.56       $1,044.4922   $1,044.48   $1,044.45   $1,044.40