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 $119.42   5.515%   $126.006   $126.01   $126.00   $126.00  
  Purchase #2 $41.98   8.526%   $45.5592   $45.56   $45.55   $45.60  
  Purchase #3 $177.49   3.718%   $184.0891   $184.09   $184.10   $184.10  
  Purchase #4 $16.53   9.323%   $18.0711   $18.07   $18.05   $18.10  
  Purchase #5 $175.50   5.421%   $185.0139   $185.01   $185.00   $185.00  
  Purchase #6 $157.51   13.817%   $179.2732   $179.27   $179.25   $179.30  
  Purchase #7 $30.61   6.696%   $32.6596   $32.66   $32.65   $32.70  
  7 purchase totals = $719.04       $770.6721   $770.67   $770.60   $770.80