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 $152.27   6.628%   $162.3625   $162.36   $162.35   $162.40  
  Purchase #2 $146.99   8.251%   $159.1181   $159.12   $159.10   $159.10  
  Purchase #3 $219.25   11.622%   $244.7312   $244.73   $244.75   $244.70  
  Purchase #4 $248.62   4.735%   $260.3922   $260.39   $260.40   $260.40  
  Purchase #5 $91.94   5.407%   $96.9112   $96.91   $96.90   $96.90  
  Purchase #6 $140.63   9.751%   $154.3428   $154.34   $154.35   $154.30  
  Purchase #7 $176.44   3.647%   $182.8748   $182.87   $182.85   $182.90  
  7 purchase totals = $1,176.14       $1,260.7328   $1,260.72   $1,260.70   $1,260.70