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 $177.72   9.852%   $195.229   $195.23   $195.25   $195.20  
  Purchase #2 $100.68   4.223%   $104.9317   $104.93   $104.95   $104.90  
  Purchase #3 $119.46   12.822%   $134.7772   $134.78   $134.80   $134.80  
  Purchase #4 $127.51   9.158%   $139.1874   $139.19   $139.20   $139.20  
  Purchase #5 $199.33   4.614%   $208.5271   $208.53   $208.55   $208.50  
  Purchase #6 $84.28   8.566%   $91.4994   $91.50   $91.50   $91.50  
  Purchase #7 $226.62   5.527%   $239.1453   $239.15   $239.15   $239.10  
  7 purchase totals = $1,035.60       $1,113.2971   $1,113.31   $1,113.40   $1,113.20