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 $168.28   3.357%   $173.9292   $173.93   $173.95   $173.90  
  Purchase #2 $13.53   11.329%   $15.0628   $15.06   $15.05   $15.10  
  Purchase #3 $202.41   3.436%   $209.3648   $209.36   $209.35   $209.40  
  Purchase #4 $23.65   9.632%   $25.928   $25.93   $25.95   $25.90  
  Purchase #5 $198.58   11.830%   $222.072   $222.07   $222.05   $222.10  
  Purchase #6 $141.81   8.736%   $154.1985   $154.20   $154.20   $154.20  
  Purchase #7 $171.36   13.509%   $194.509   $194.51   $194.50   $194.50  
  7 purchase totals = $919.62       $995.0643   $995.06   $995.05   $995.10