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 $164.57   7.267%   $176.5293   $176.53   $176.55   $176.50  
  Purchase #2 $24.42   11.826%   $27.3079   $27.31   $27.30   $27.30  
  Purchase #3 $118.90   10.751%   $131.6829   $131.68   $131.70   $131.70  
  Purchase #4 $95.33   8.424%   $103.3606   $103.36   $103.35   $103.40  
  Purchase #5 $8.76   9.774%   $9.6162   $9.62   $9.60   $9.60  
  Purchase #6 $205.51   7.247%   $220.4033   $220.40   $220.40   $220.40  
  Purchase #7 $250.51   13.569%   $284.5017   $284.50   $284.50   $284.50  
  7 purchase totals = $868.00       $953.4019   $953.40   $953.40   $953.40