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 $183.97   6.833%   $196.5407   $196.54   $196.55   $196.50  
  Purchase #2 $86.87   13.530%   $98.6235   $98.62   $98.60   $98.60  
  Purchase #3 $22.49   3.637%   $23.308   $23.31   $23.30   $23.30  
  Purchase #4 $109.95   9.334%   $120.2127   $120.21   $120.20   $120.20  
  Purchase #5 $51.62   5.715%   $54.5701   $54.57   $54.55   $54.60  
  Purchase #6 $206.25   5.539%   $217.6742   $217.67   $217.65   $217.70  
  Purchase #7 $14.50   7.709%   $15.6178   $15.62   $15.60   $15.60  
  7 purchase totals = $675.65       $726.5470   $726.54   $726.45   $726.50