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 $208.26   8.465%   $225.8892   $225.89   $225.90   $225.90  
  Purchase #2 $164.95   13.148%   $186.6376   $186.64   $186.65   $186.60  
  Purchase #3 $46.48   4.857%   $48.7375   $48.74   $48.75   $48.70  
  Purchase #4 $198.40   5.605%   $209.5203   $209.52   $209.50   $209.50  
  Purchase #5 $113.40   10.469%   $125.2718   $125.27   $125.25   $125.30  
  Purchase #6 $189.84   6.749%   $202.6523   $202.65   $202.65   $202.70  
  Purchase #7 $14.36   10.733%   $15.9013   $15.90   $15.90   $15.90  
  7 purchase totals = $935.69       $1,014.6100   $1,014.61   $1,014.60   $1,014.60