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 $208.61   3.551%   $216.0177   $216.02   $216.00   $216.00  
  Purchase #2 $187.63   8.222%   $203.0569   $203.06   $203.05   $203.10  
  Purchase #3 $118.62   5.386%   $125.0089   $125.01   $125.00   $125.00  
  Purchase #4 $185.99   6.473%   $198.0291   $198.03   $198.05   $198.00  
  Purchase #5 $20.55   12.735%   $23.167   $23.17   $23.15   $23.20  
  Purchase #6 $71.67   10.335%   $79.0771   $79.08   $79.10   $79.10  
  Purchase #7 $66.74   8.814%   $72.6225   $72.62   $72.60   $72.60  
  7 purchase totals = $859.81       $916.9792   $916.99   $916.95   $917.00