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 $36.54   13.162%   $41.3494   $41.35   $41.35   $41.30  
  Purchase #2 $248.61   4.794%   $260.5284   $260.53   $260.55   $260.50  
  Purchase #3 $146.37   8.235%   $158.4236   $158.42   $158.40   $158.40  
  Purchase #4 $244.51   5.273%   $257.403   $257.40   $257.40   $257.40  
  Purchase #5 $250.37   6.754%   $267.28   $267.28   $267.30   $267.30  
  Purchase #6 $165.45   13.397%   $187.6153   $187.62   $187.60   $187.60  
  Purchase #7 $28.84   12.411%   $32.4193   $32.42   $32.40   $32.40  
  7 purchase totals = $1,120.69       $1,205.0190   $1,205.02   $1,205.00   $1,204.90