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 $196.51   5.298%   $206.9211   $206.92   $206.90   $206.90  
  Purchase #2 $62.53   11.646%   $69.8122   $69.81   $69.80   $69.80  
  Purchase #3 $242.83   5.470%   $256.1128   $256.11   $256.10   $256.10  
  Purchase #4 $96.49   9.586%   $105.7395   $105.74   $105.75   $105.70  
  Purchase #5 $201.69   11.269%   $224.4184   $224.42   $224.40   $224.40  
  Purchase #6 $117.87   10.868%   $130.6801   $130.68   $130.70   $130.70  
  Purchase #7 $245.69   8.538%   $266.667   $266.67   $266.65   $266.70  
  7 purchase totals = $1,163.61       $1,260.3511   $1,260.35   $1,260.30   $1,260.30