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 $118.25   7.866%   $127.5515   $127.55   $127.55   $127.60  
  Purchase #2 $60.41   6.583%   $64.3868   $64.39   $64.40   $64.40  
  Purchase #3 $191.86   8.115%   $207.4294   $207.43   $207.45   $207.40  
  Purchase #4 $223.92   9.407%   $244.9842   $244.98   $245.00   $245.00  
  Purchase #5 $100.45   13.291%   $113.8008   $113.80   $113.80   $113.80  
  Purchase #6 $102.92   11.353%   $114.6045   $114.60   $114.60   $114.60  
  Purchase #7 $11.28   4.236%   $11.7578   $11.76   $11.75   $11.80  
  7 purchase totals = $809.09       $884.5150   $884.51   $884.55   $884.60