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 $182.29   10.343%   $201.1443   $201.14   $201.15   $201.10  
  Purchase #2 $41.77   7.195%   $44.7754   $44.78   $44.80   $44.80  
  Purchase #3 $11.47   3.567%   $11.8791   $11.88   $11.90   $11.90  
  Purchase #4 $94.30   8.403%   $102.224   $102.22   $102.20   $102.20  
  Purchase #5 $52.48   12.487%   $59.0332   $59.03   $59.05   $59.00  
  Purchase #6 $163.65   8.629%   $177.7714   $177.77   $177.75   $177.80  
  Purchase #7 $175.48   13.501%   $199.1716   $199.17   $199.15   $199.20  
  7 purchase totals = $721.44       $795.9990   $795.99   $796.00   $796.00