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 $38.67   6.475%   $41.1739   $41.17   $41.15   $41.20  
  Purchase #2 $232.66   5.773%   $246.0915   $246.09   $246.10   $246.10  
  Purchase #3 $237.67   5.847%   $251.5666   $251.57   $251.55   $251.60  
  Purchase #4 $28.83   5.605%   $30.4459   $30.45   $30.45   $30.40  
  Purchase #5 $188.97   5.284%   $198.9552   $198.96   $198.95   $199.00  
  Purchase #6 $197.35   5.534%   $208.2713   $208.27   $208.25   $208.30  
  Purchase #7 $164.42   9.267%   $179.6568   $179.66   $179.65   $179.70  
  7 purchase totals = $1,088.57       $1,156.1612   $1,156.17   $1,156.10   $1,156.30