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 $72.81   4.391%   $76.0071   $76.01   $76.00   $76.00  
  Purchase #2 $107.40   6.752%   $114.6516   $114.65   $114.65   $114.70  
  Purchase #3 $240.98   5.819%   $255.0026   $255.00   $255.00   $255.00  
  Purchase #4 $79.51   9.408%   $86.9903   $86.99   $87.00   $87.00  
  Purchase #5 $38.87   9.812%   $42.6839   $42.68   $42.70   $42.70  
  Purchase #6 $163.70   6.108%   $173.6988   $173.70   $173.70   $173.70  
  Purchase #7 $193.84   4.498%   $202.5589   $202.56   $202.55   $202.60  
  7 purchase totals = $897.11       $951.5932   $951.59   $951.60   $951.70