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 $213.43   9.175%   $233.0122   $233.01   $233.00   $233.00  
  Purchase #2 $224.39   8.601%   $243.6898   $243.69   $243.70   $243.70  
  Purchase #3 $72.34   5.425%   $76.2644   $76.26   $76.25   $76.30  
  Purchase #4 $54.71   5.418%   $57.6742   $57.67   $57.65   $57.70  
  Purchase #5 $117.25   5.542%   $123.748   $123.75   $123.75   $123.70  
  Purchase #6 $108.34   6.407%   $115.2813   $115.28   $115.30   $115.30  
  Purchase #7 $150.43   8.704%   $163.5234   $163.52   $163.50   $163.50  
  7 purchase totals = $940.89       $1,013.1933   $1,013.18   $1,013.15   $1,013.20