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 $110.98   13.738%   $126.2264   $126.23   $126.25   $126.20  
  Purchase #2 $71.59   7.460%   $76.9306   $76.93   $76.95   $76.90  
  Purchase #3 $229.70   4.542%   $240.133   $240.13   $240.15   $240.10  
  Purchase #4 $177.64   3.130%   $183.2001   $183.20   $183.20   $183.20  
  Purchase #5 $86.94   9.744%   $95.4114   $95.41   $95.40   $95.40  
  Purchase #6 $187.44   7.179%   $200.8963   $200.90   $200.90   $200.90  
  Purchase #7 $161.97   7.308%   $173.8068   $173.81   $173.80   $173.80  
  7 purchase totals = $1,026.26       $1,096.6046   $1,096.61   $1,096.65   $1,096.50