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 $244.51   5.361%   $257.6182   $257.62   $257.60   $257.60  
  Purchase #2 $59.99   4.471%   $62.6722   $62.67   $62.65   $62.70  
  Purchase #3 $194.74   4.772%   $204.033   $204.03   $204.05   $204.00  
  Purchase #4 $32.90   8.487%   $35.6922   $35.69   $35.70   $35.70  
  Purchase #5 $216.27   6.771%   $230.9136   $230.91   $230.90   $230.90  
  Purchase #6 $101.71   12.374%   $114.2956   $114.30   $114.30   $114.30  
  Purchase #7 $193.39   5.723%   $204.4577   $204.46   $204.45   $204.50  
  7 purchase totals = $1,043.51       $1,109.6825   $1,109.68   $1,109.65   $1,109.70