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 $140.48   8.392%   $152.2691   $152.27   $152.25   $152.30  
  Purchase #2 $95.57   11.689%   $106.7412   $106.74   $106.75   $106.70  
  Purchase #3 $104.39   9.856%   $114.6787   $114.68   $114.70   $114.70  
  Purchase #4 $189.62   6.176%   $201.3309   $201.33   $201.35   $201.30  
  Purchase #5 $226.39   11.410%   $252.2211   $252.22   $252.20   $252.20  
  Purchase #6 $26.29   5.222%   $27.6629   $27.66   $27.65   $27.70  
  Purchase #7 $200.93   6.872%   $214.7379   $214.74   $214.75   $214.70  
  7 purchase totals = $983.67       $1,069.6418   $1,069.64   $1,069.65   $1,069.60