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 $227.48   7.837%   $245.3076   $245.31   $245.30   $245.30  
  Purchase #2 $71.69   6.286%   $76.1964   $76.20   $76.20   $76.20  
  Purchase #3 $83.84   4.393%   $87.5231   $87.52   $87.50   $87.50  
  Purchase #4 $183.62   5.589%   $193.8825   $193.88   $193.90   $193.90  
  Purchase #5 $78.70   9.593%   $86.2497   $86.25   $86.25   $86.20  
  Purchase #6 $213.25   3.489%   $220.6903   $220.69   $220.70   $220.70  
  Purchase #7 $46.81   11.589%   $52.2348   $52.23   $52.25   $52.20  
  7 purchase totals = $905.39       $962.0844   $962.08   $962.10   $962.00