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 $196.48   4.636%   $205.5888   $205.59   $205.60   $205.60  
  Purchase #2 $85.57   9.305%   $93.5323   $93.53   $93.55   $93.50  
  Purchase #3 $164.29   8.241%   $177.8291   $177.83   $177.85   $177.80  
  Purchase #4 $24.53   12.697%   $27.6446   $27.64   $27.65   $27.60  
  Purchase #5 $138.79   11.456%   $154.6898   $154.69   $154.70   $154.70  
  Purchase #6 $157.39   3.382%   $162.7129   $162.71   $162.70   $162.70  
  Purchase #7 $206.54   11.460%   $230.2095   $230.21   $230.20   $230.20  
  7 purchase totals = $973.59       $1,052.2070   $1,052.20   $1,052.25   $1,052.10