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 $60.77   6.473%   $64.7036   $64.70   $64.70   $64.70  
  Purchase #2 $161.95   8.648%   $175.9554   $175.96   $175.95   $176.00  
  Purchase #3 $136.55   10.759%   $151.2414   $151.24   $151.25   $151.20  
  Purchase #4 $38.61   7.391%   $41.4637   $41.46   $41.45   $41.50  
  Purchase #5 $208.61   7.833%   $224.9504   $224.95   $224.95   $225.00  
  Purchase #6 $159.45   8.758%   $173.4146   $173.41   $173.40   $173.40  
  Purchase #7 $179.30   12.194%   $201.1638   $201.16   $201.15   $201.20  
  7 purchase totals = $945.24       $1,032.8929   $1,032.88   $1,032.85   $1,033.00