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 $35.26   5.853%   $37.3238   $37.32   $37.30   $37.30  
  Purchase #2 $209.46   11.333%   $233.1981   $233.20   $233.20   $233.20  
  Purchase #3 $119.81   13.589%   $136.091   $136.09   $136.10   $136.10  
  Purchase #4 $200.37   10.645%   $221.6994   $221.70   $221.70   $221.70  
  Purchase #5 $55.96   10.165%   $61.6483   $61.65   $61.65   $61.60  
  Purchase #6 $201.92   10.445%   $223.0105   $223.01   $223.00   $223.00  
  Purchase #7 $44.45   11.794%   $49.6924   $49.69   $49.70   $49.70  
  7 purchase totals = $867.23       $962.6635   $962.66   $962.65   $962.60