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 $212.91   8.163%   $230.2898   $230.29   $230.30   $230.30  
  Purchase #2 $216.55   8.836%   $235.6844   $235.68   $235.70   $235.70  
  Purchase #3 $27.34   11.388%   $30.4535   $30.45   $30.45   $30.50  
  Purchase #4 $113.72   5.119%   $119.5413   $119.54   $119.55   $119.50  
  Purchase #5 $219.41   9.536%   $240.3329   $240.33   $240.35   $240.30  
  Purchase #6 $82.59   5.208%   $86.8913   $86.89   $86.90   $86.90  
  Purchase #7 $249.87   5.505%   $263.6253   $263.63   $263.65   $263.60  
  7 purchase totals = $1,122.39       $1,206.8185   $1,206.81   $1,206.90   $1,206.80