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 $107.69   4.493%   $112.5285   $112.53   $112.55   $112.50  
  Purchase #2 $151.76   7.138%   $162.5926   $162.59   $162.60   $162.60  
  Purchase #3 $215.66   6.640%   $229.9798   $229.98   $230.00   $230.00  
  Purchase #4 $200.27   3.765%   $207.8102   $207.81   $207.80   $207.80  
  Purchase #5 $56.81   7.844%   $61.2662   $61.27   $61.25   $61.30  
  Purchase #6 $8.83   8.206%   $9.5546   $9.55   $9.55   $9.60  
  Purchase #7 $104.44   7.266%   $112.0286   $112.03   $112.05   $112.00  
  7 purchase totals = $845.46       $895.7605   $895.76   $895.80   $895.80