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 $104.41   9.202%   $114.0178   $114.02   $114.00   $114.00  
  Purchase #2 $104.45   9.379%   $114.2464   $114.25   $114.25   $114.20  
  Purchase #3 $118.65   6.851%   $126.7787   $126.78   $126.80   $126.80  
  Purchase #4 $107.84   10.172%   $118.8095   $118.81   $118.80   $118.80  
  Purchase #5 $164.51   6.542%   $175.2722   $175.27   $175.25   $175.30  
  Purchase #6 $96.43   10.731%   $106.7779   $106.78   $106.80   $106.80  
  Purchase #7 $49.56   12.427%   $55.7188   $55.72   $55.70   $55.70  
  7 purchase totals = $745.85       $811.6213   $811.63   $811.60   $811.60