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 $197.82   5.440%   $208.5814   $208.58   $208.60   $208.60  
  Purchase #2 $162.46   6.113%   $172.3912   $172.39   $172.40   $172.40  
  Purchase #3 $153.34   8.417%   $166.2466   $166.25   $166.25   $166.20  
  Purchase #4 $248.66   7.296%   $266.8022   $266.80   $266.80   $266.80  
  Purchase #5 $182.47   12.174%   $204.6839   $204.68   $204.70   $204.70  
  Purchase #6 $44.45   6.855%   $47.497   $47.50   $47.50   $47.50  
  Purchase #7 $159.52   11.613%   $178.0451   $178.05   $178.05   $178.00  
  7 purchase totals = $1,148.72       $1,244.2474   $1,244.25   $1,244.30   $1,244.20