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 $44.27   11.131%   $49.1977   $49.20   $49.20   $49.20  
  Purchase #2 $124.81   4.730%   $130.7135   $130.71   $130.70   $130.70  
  Purchase #3 $61.71   5.580%   $65.1534   $65.15   $65.15   $65.20  
  Purchase #4 $187.97   10.793%   $208.2576   $208.26   $208.25   $208.30  
  Purchase #5 $202.99   10.774%   $224.8601   $224.86   $224.85   $224.90  
  Purchase #6 $186.26   10.592%   $205.9887   $205.99   $206.00   $206.00  
  Purchase #7 $206.45   7.830%   $222.615   $222.62   $222.60   $222.60  
  7 purchase totals = $1,014.46       $1,106.7860   $1,106.79   $1,106.75   $1,106.90