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 $190.84   4.776%   $199.9545   $199.95   $199.95   $200.00  
  Purchase #2 $234.93   13.851%   $267.4702   $267.47   $267.45   $267.50  
  Purchase #3 $25.48   12.349%   $28.6265   $28.63   $28.65   $28.60  
  Purchase #4 $65.77   4.286%   $68.5889   $68.59   $68.60   $68.60  
  Purchase #5 $46.81   12.396%   $52.6126   $52.61   $52.60   $52.60  
  Purchase #6 $106.25   7.855%   $114.5959   $114.60   $114.60   $114.60  
  Purchase #7 $13.43   6.750%   $14.3365   $14.34   $14.35   $14.30  
  7 purchase totals = $683.51       $746.1851   $746.19   $746.20   $746.20