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 $63.62   9.325%   $69.5526   $69.55   $69.55   $69.60  
  Purchase #2 $196.35   9.844%   $215.6787   $215.68   $215.70   $215.70  
  Purchase #3 $166.31   8.354%   $180.2035   $180.20   $180.20   $180.20  
  Purchase #4 $61.75   3.642%   $63.9989   $64.00   $64.00   $64.00  
  Purchase #5 $139.75   8.544%   $151.6902   $151.69   $151.70   $151.70  
  Purchase #6 $81.75   5.413%   $86.1751   $86.18   $86.20   $86.20  
  Purchase #7 $199.25   8.241%   $215.6702   $215.67   $215.65   $215.70  
  7 purchase totals = $908.78       $982.9692   $982.97   $983.00   $983.10