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 $31.47   5.581%   $33.2263   $33.23   $33.25   $33.20  
  Purchase #2 $106.96   7.193%   $114.6536   $114.65   $114.65   $114.70  
  Purchase #3 $166.57   7.142%   $178.4664   $178.47   $178.45   $178.50  
  Purchase #4 $91.32   7.598%   $98.2585   $98.26   $98.25   $98.30  
  Purchase #5 $163.26   12.583%   $183.803   $183.80   $183.80   $183.80  
  Purchase #6 $115.48   9.758%   $126.7485   $126.75   $126.75   $126.70  
  Purchase #7 $204.98   3.535%   $212.226   $212.23   $212.25   $212.20  
  7 purchase totals = $880.04       $947.3823   $947.39   $947.40   $947.40