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 $69.82   5.580%   $73.716   $73.72   $73.70   $73.70  
  Purchase #2 $210.95   3.492%   $218.3164   $218.32   $218.30   $218.30  
  Purchase #3 $151.81   7.265%   $162.839   $162.84   $162.85   $162.80  
  Purchase #4 $190.97   5.518%   $201.5077   $201.51   $201.50   $201.50  
  Purchase #5 $32.66   7.687%   $35.1706   $35.17   $35.15   $35.20  
  Purchase #6 $47.76   12.329%   $53.6483   $53.65   $53.65   $53.60  
  Purchase #7 $72.65   6.142%   $77.1122   $77.11   $77.10   $77.10  
  7 purchase totals = $776.62       $822.3102   $822.32   $822.25   $822.20