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 $56.53   4.698%   $59.1858   $59.19   $59.20   $59.20  
  Purchase #2 $126.28   4.656%   $132.1596   $132.16   $132.15   $132.20  
  Purchase #3 $153.81   12.297%   $172.724   $172.72   $172.70   $172.70  
  Purchase #4 $243.65   8.268%   $263.795   $263.80   $263.80   $263.80  
  Purchase #5 $60.95   13.110%   $68.9405   $68.94   $68.95   $68.90  
  Purchase #6 $214.39   11.589%   $239.2357   $239.24   $239.25   $239.20  
  Purchase #7 $237.43   10.232%   $261.7238   $261.72   $261.70   $261.70  
  7 purchase totals = $1,093.04       $1,197.7644   $1,197.77   $1,197.75   $1,197.70