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 $200.48   6.815%   $214.1427   $214.14   $214.15   $214.10  
  Purchase #2 $168.91   11.675%   $188.6302   $188.63   $188.65   $188.60  
  Purchase #3 $57.31   8.572%   $62.2226   $62.22   $62.20   $62.20  
  Purchase #4 $160.62   6.616%   $171.2466   $171.25   $171.25   $171.20  
  Purchase #5 $133.81   5.857%   $141.6473   $141.65   $141.65   $141.60  
  Purchase #6 $241.34   12.505%   $271.5196   $271.52   $271.50   $271.50  
  Purchase #7 $100.71   4.102%   $104.8411   $104.84   $104.85   $104.80  
  7 purchase totals = $1,063.18       $1,154.2501   $1,154.25   $1,154.25   $1,154.00