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 $114.67   10.494%   $126.7035   $126.70   $126.70   $126.70  
  Purchase #2 $74.61   9.802%   $81.9233   $81.92   $81.90   $81.90  
  Purchase #3 $224.79   7.485%   $241.6155   $241.62   $241.60   $241.60  
  Purchase #4 $175.67   7.390%   $188.652   $188.65   $188.65   $188.70  
  Purchase #5 $190.66   5.499%   $201.1444   $201.14   $201.15   $201.10  
  Purchase #6 $187.86   9.159%   $205.0661   $205.07   $205.05   $205.10  
  Purchase #7 $87.45   9.182%   $95.4797   $95.48   $95.50   $95.50  
  7 purchase totals = $1,055.71       $1,140.5845   $1,140.58   $1,140.55   $1,140.60