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 $87.68   8.302%   $94.9592   $94.96   $94.95   $95.00  
  Purchase #2 $186.81   6.140%   $198.2801   $198.28   $198.30   $198.30  
  Purchase #3 $68.53   4.202%   $71.4096   $71.41   $71.40   $71.40  
  Purchase #4 $48.46   8.187%   $52.4274   $52.43   $52.45   $52.40  
  Purchase #5 $139.43   4.397%   $145.5607   $145.56   $145.55   $145.60  
  Purchase #6 $129.45   3.815%   $134.3885   $134.39   $134.40   $134.40  
  Purchase #7 $203.58   4.715%   $213.1788   $213.18   $213.20   $213.20  
  7 purchase totals = $863.94       $910.2043   $910.21   $910.25   $910.30