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 $187.66   3.749%   $194.6954   $194.70   $194.70   $194.70  
  Purchase #2 $175.80   8.177%   $190.1752   $190.18   $190.20   $190.20  
  Purchase #3 $16.51   7.138%   $17.6885   $17.69   $17.70   $17.70  
  Purchase #4 $100.96   5.401%   $106.4128   $106.41   $106.40   $106.40  
  Purchase #5 $250.91   6.542%   $267.3245   $267.32   $267.30   $267.30  
  Purchase #6 $59.90   7.587%   $64.4446   $64.44   $64.45   $64.40  
  Purchase #7 $158.92   10.849%   $176.1612   $176.16   $176.15   $176.20  
  7 purchase totals = $950.66       $1,016.9022   $1,016.90   $1,016.90   $1,016.90