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 $182.25   4.646%   $190.7173   $190.72   $190.70   $190.70  
  Purchase #2 $6.74   7.325%   $7.2337   $7.23   $7.25   $7.20  
  Purchase #3 $51.35   12.526%   $57.7821   $57.78   $57.80   $57.80  
  Purchase #4 $46.43   3.227%   $47.9283   $47.93   $47.95   $47.90  
  Purchase #5 $208.52   7.747%   $224.674   $224.67   $224.65   $224.70  
  Purchase #6 $152.71   7.685%   $164.4458   $164.45   $164.45   $164.40  
  Purchase #7 $58.66   12.759%   $66.1444   $66.14   $66.15   $66.10  
  7 purchase totals = $706.66       $758.9256   $758.92   $758.95   $758.80