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 $34.59   5.412%   $36.462   $36.46   $36.45   $36.50  
  Purchase #2 $191.42   4.301%   $199.653   $199.65   $199.65   $199.70  
  Purchase #3 $226.66   9.516%   $248.229   $248.23   $248.25   $248.20  
  Purchase #4 $184.28   9.853%   $202.4371   $202.44   $202.45   $202.40  
  Purchase #5 $85.90   9.520%   $94.0777   $94.08   $94.10   $94.10  
  Purchase #6 $168.70   12.732%   $190.1789   $190.18   $190.20   $190.20  
  Purchase #7 $222.66   10.648%   $246.3688   $246.37   $246.35   $246.40  
  7 purchase totals = $1,114.21       $1,217.4065   $1,217.41   $1,217.45   $1,217.50