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 $119.81   5.872%   $126.8452   $126.85   $126.85   $126.80  
  Purchase #2 $93.65   11.102%   $104.047   $104.05   $104.05   $104.00  
  Purchase #3 $207.25   9.362%   $226.6527   $226.65   $226.65   $226.70  
  Purchase #4 $219.64   13.137%   $248.4941   $248.49   $248.50   $248.50  
  Purchase #5 $167.93   8.645%   $182.4475   $182.45   $182.45   $182.40  
  Purchase #6 $242.97   10.195%   $267.7408   $267.74   $267.75   $267.70  
  Purchase #7 $233.91   12.322%   $262.7324   $262.73   $262.75   $262.70  
  7 purchase totals = $1,285.16       $1,418.9597   $1,418.96   $1,419.00   $1,418.80