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 $88.43   7.697%   $95.2365   $95.24   $95.25   $95.20  
  Purchase #2 $237.61   8.423%   $257.6239   $257.62   $257.60   $257.60  
  Purchase #3 $14.64   3.407%   $15.1388   $15.14   $15.15   $15.10  
  Purchase #4 $120.83   3.161%   $124.6494   $124.65   $124.65   $124.60  
  Purchase #5 $167.53   11.290%   $186.4441   $186.44   $186.45   $186.40  
  Purchase #6 $208.34   12.560%   $234.5075   $234.51   $234.50   $234.50  
  Purchase #7 $6.97   6.643%   $7.433   $7.43   $7.45   $7.40  
  7 purchase totals = $844.35       $921.0332   $921.03   $921.05   $920.80