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 $116.32   8.533%   $126.2456   $126.25   $126.25   $126.20  
  Purchase #2 $97.34   10.176%   $107.2453   $107.25   $107.25   $107.20  
  Purchase #3 $14.25   5.567%   $15.0433   $15.04   $15.05   $15.00  
  Purchase #4 $102.35   13.518%   $116.1857   $116.19   $116.20   $116.20  
  Purchase #5 $209.49   8.103%   $226.465   $226.47   $226.45   $226.50  
  Purchase #6 $72.77   9.633%   $79.7799   $79.78   $79.80   $79.80  
  Purchase #7 $174.87   5.682%   $184.8061   $184.81   $184.80   $184.80  
  7 purchase totals = $787.39       $855.7709   $855.79   $855.80   $855.70