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 $175.82   8.685%   $191.09   $191.09   $191.10   $191.10  
  Purchase #2 $240.31   11.277%   $267.4098   $267.41   $267.40   $267.40  
  Purchase #3 $197.32   3.737%   $204.6938   $204.69   $204.70   $204.70  
  Purchase #4 $155.28   5.310%   $163.5254   $163.53   $163.55   $163.50  
  Purchase #5 $143.81   11.316%   $160.0835   $160.08   $160.10   $160.10  
  Purchase #6 $248.44   13.793%   $282.7073   $282.71   $282.70   $282.70  
  Purchase #7 $205.58   10.400%   $226.9603   $226.96   $226.95   $227.00  
  7 purchase totals = $1,366.56       $1,496.4701   $1,496.47   $1,496.50   $1,496.50