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 $192.54   11.609%   $214.892   $214.89   $214.90   $214.90  
  Purchase #2 $73.63   4.245%   $76.7556   $76.76   $76.75   $76.80  
  Purchase #3 $201.92   12.229%   $226.6128   $226.61   $226.60   $226.60  
  Purchase #4 $82.49   4.199%   $85.9538   $85.95   $85.95   $86.00  
  Purchase #5 $69.89   9.547%   $76.5624   $76.56   $76.55   $76.60  
  Purchase #6 $242.30   10.609%   $268.0056   $268.01   $268.00   $268.00  
  Purchase #7 $70.85   7.803%   $76.3784   $76.38   $76.40   $76.40  
  7 purchase totals = $933.62       $1,025.1606   $1,025.16   $1,025.15   $1,025.30