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 $52.33   13.631%   $59.4631   $59.46   $59.45   $59.50  
  Purchase #2 $211.60   3.772%   $219.5816   $219.58   $219.60   $219.60  
  Purchase #3 $30.28   12.660%   $34.1134   $34.11   $34.10   $34.10  
  Purchase #4 $193.60   6.594%   $206.366   $206.37   $206.35   $206.40  
  Purchase #5 $163.64   6.342%   $174.018   $174.02   $174.00   $174.00  
  Purchase #6 $221.28   12.239%   $248.3625   $248.36   $248.35   $248.40  
  Purchase #7 $124.48   9.825%   $136.7102   $136.71   $136.70   $136.70  
  7 purchase totals = $997.21       $1,078.6148   $1,078.61   $1,078.55   $1,078.70