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 $106.87   6.722%   $114.0538   $114.05   $114.05   $114.10  
  Purchase #2 $183.87   13.191%   $208.1243   $208.12   $208.10   $208.10  
  Purchase #3 $80.86   9.774%   $88.7633   $88.76   $88.75   $88.80  
  Purchase #4 $153.51   8.622%   $166.7456   $166.75   $166.75   $166.70  
  Purchase #5 $106.25   9.520%   $116.365   $116.37   $116.35   $116.40  
  Purchase #6 $160.25   9.380%   $175.2815   $175.28   $175.30   $175.30  
  Purchase #7 $230.87   4.771%   $241.8848   $241.88   $241.90   $241.90  
  7 purchase totals = $1,022.48       $1,111.2183   $1,111.21   $1,111.20   $1,111.30