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 $114.46   10.474%   $126.4485   $126.45   $126.45   $126.40  
  Purchase #2 $103.68   12.221%   $116.3507   $116.35   $116.35   $116.40  
  Purchase #3 $181.53   9.383%   $198.563   $198.56   $198.55   $198.60  
  Purchase #4 $217.56   5.839%   $230.2633   $230.26   $230.25   $230.30  
  Purchase #5 $156.61   7.549%   $168.4325   $168.43   $168.45   $168.40  
  Purchase #6 $105.35   13.345%   $119.409   $119.41   $119.40   $119.40  
  Purchase #7 $127.55   12.292%   $143.2284   $143.23   $143.25   $143.20  
  7 purchase totals = $1,006.74       $1,102.6954   $1,102.69   $1,102.70   $1,102.70