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 $111.88   5.152%   $117.6441   $117.64   $117.65   $117.60  
  Purchase #2 $54.54   10.641%   $60.3436   $60.34   $60.35   $60.30  
  Purchase #3 $153.33   9.795%   $168.3487   $168.35   $168.35   $168.30  
  Purchase #4 $67.91   10.402%   $74.974   $74.97   $74.95   $75.00  
  Purchase #5 $182.66   6.704%   $194.9055   $194.91   $194.90   $194.90  
  Purchase #6 $246.67   8.800%   $268.377   $268.38   $268.40   $268.40  
  Purchase #7 $44.54   3.383%   $46.0468   $46.05   $46.05   $46.00  
  7 purchase totals = $861.53       $930.6397   $930.64   $930.65   $930.50