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 $151.56   7.293%   $162.6133   $162.61   $162.60   $162.60  
  Purchase #2 $173.54   7.191%   $186.0193   $186.02   $186.00   $186.00  
  Purchase #3 $63.37   7.292%   $67.9909   $67.99   $68.00   $68.00  
  Purchase #4 $11.71   6.425%   $12.4624   $12.46   $12.45   $12.50  
  Purchase #5 $190.45   8.292%   $206.2421   $206.24   $206.25   $206.20  
  Purchase #6 $223.43   9.573%   $244.819   $244.82   $244.80   $244.80  
  Purchase #7 $196.66   10.615%   $217.5355   $217.54   $217.55   $217.50  
  7 purchase totals = $1,010.72       $1,097.6825   $1,097.68   $1,097.65   $1,097.60