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 $96.69   8.253%   $104.6698   $104.67   $104.65   $104.70  
  Purchase #2 $34.51   3.794%   $35.8193   $35.82   $35.80   $35.80  
  Purchase #3 $95.68   4.311%   $99.8048   $99.80   $99.80   $99.80  
  Purchase #4 $25.63   9.600%   $28.0905   $28.09   $28.10   $28.10  
  Purchase #5 $175.34   11.735%   $195.9161   $195.92   $195.90   $195.90  
  Purchase #6 $16.97   8.633%   $18.435   $18.44   $18.45   $18.40  
  Purchase #7 $245.89   6.667%   $262.2835   $262.28   $262.30   $262.30  
  7 purchase totals = $690.71       $745.0190   $745.02   $745.00   $745.00