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 $202.63   5.604%   $213.9854   $213.99   $214.00   $214.00  
  Purchase #2 $30.59   9.546%   $33.5101   $33.51   $33.50   $33.50  
  Purchase #3 $41.64   6.257%   $44.2454   $44.25   $44.25   $44.20  
  Purchase #4 $96.35   10.544%   $106.5091   $106.51   $106.50   $106.50  
  Purchase #5 $124.55   5.164%   $130.9818   $130.98   $131.00   $131.00  
  Purchase #6 $186.77   8.745%   $203.103   $203.10   $203.10   $203.10  
  Purchase #7 $75.48   5.442%   $79.5876   $79.59   $79.60   $79.60  
  7 purchase totals = $758.01       $811.9224   $811.93   $811.95   $811.90