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 $58.80   6.273%   $62.4885   $62.49   $62.50   $62.50  
  Purchase #2 $173.99   4.777%   $182.3015   $182.30   $182.30   $182.30  
  Purchase #3 $62.51   6.464%   $66.5506   $66.55   $66.55   $66.60  
  Purchase #4 $86.41   12.681%   $97.3677   $97.37   $97.35   $97.40  
  Purchase #5 $214.76   8.668%   $233.3754   $233.38   $233.40   $233.40  
  Purchase #6 $248.72   5.401%   $262.1534   $262.15   $262.15   $262.20  
  Purchase #7 $204.78   9.598%   $224.4348   $224.43   $224.45   $224.40  
  7 purchase totals = $1,049.97       $1,128.6719   $1,128.67   $1,128.70   $1,128.80