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 $196.83   9.717%   $215.956   $215.96   $215.95   $216.00  
  Purchase #2 $118.62   11.728%   $132.5318   $132.53   $132.55   $132.50  
  Purchase #3 $228.71   4.801%   $239.6904   $239.69   $239.70   $239.70  
  Purchase #4 $179.60   10.462%   $198.3898   $198.39   $198.40   $198.40  
  Purchase #5 $91.54   3.567%   $94.8052   $94.81   $94.80   $94.80  
  Purchase #6 $96.40   7.129%   $103.2724   $103.27   $103.25   $103.30  
  Purchase #7 $12.56   9.720%   $13.7808   $13.78   $13.80   $13.80  
  7 purchase totals = $924.26       $998.4264   $998.43   $998.45   $998.50