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 $179.96   9.567%   $197.1768   $197.18   $197.20   $197.20  
  Purchase #2 $172.59   13.653%   $196.1537   $196.15   $196.15   $196.20  
  Purchase #3 $59.68   8.849%   $64.9611   $64.96   $64.95   $65.00  
  Purchase #4 $178.79   12.421%   $200.9975   $201.00   $201.00   $201.00  
  Purchase #5 $139.32   4.537%   $145.6409   $145.64   $145.65   $145.60  
  Purchase #6 $104.98   8.508%   $113.9117   $113.91   $113.90   $113.90  
  Purchase #7 $13.99   8.220%   $15.14   $15.14   $15.15   $15.10  
  7 purchase totals = $849.31       $933.9817   $933.98   $934.00   $934.00