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 $114.75   3.663%   $118.9533   $118.95   $118.95   $119.00  
  Purchase #2 $206.81   7.154%   $221.6052   $221.61   $221.60   $221.60  
  Purchase #3 $30.41   6.780%   $32.4718   $32.47   $32.45   $32.50  
  Purchase #4 $127.78   5.336%   $134.5983   $134.60   $134.60   $134.60  
  Purchase #5 $205.88   4.728%   $215.614   $215.61   $215.60   $215.60  
  Purchase #6 $147.99   3.237%   $152.7804   $152.78   $152.80   $152.80  
  Purchase #7 $157.82   5.615%   $166.6816   $166.68   $166.70   $166.70  
  7 purchase totals = $991.44       $1,042.7046   $1,042.70   $1,042.70   $1,042.80