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 $66.61   4.704%   $69.7433   $69.74   $69.75   $69.70  
  Purchase #2 $246.32   5.418%   $259.6656   $259.67   $259.65   $259.70  
  Purchase #3 $55.47   4.580%   $58.0105   $58.01   $58.00   $58.00  
  Purchase #4 $99.87   8.468%   $108.327   $108.33   $108.35   $108.30  
  Purchase #5 $87.39   6.493%   $93.0642   $93.06   $93.05   $93.10  
  Purchase #6 $177.65   5.574%   $187.5522   $187.55   $187.55   $187.60  
  Purchase #7 $230.96   10.856%   $256.033   $256.03   $256.05   $256.00  
  7 purchase totals = $964.27       $1,032.3958   $1,032.39   $1,032.40   $1,032.40