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 $55.61   11.577%   $62.048   $62.05   $62.05   $62.00  
  Purchase #2 $115.53   7.833%   $124.5795   $124.58   $124.60   $124.60  
  Purchase #3 $15.38   6.387%   $16.3623   $16.36   $16.35   $16.40  
  Purchase #4 $31.58   10.745%   $34.9733   $34.97   $34.95   $35.00  
  Purchase #5 $87.69   3.470%   $90.7328   $90.73   $90.75   $90.70  
  Purchase #6 $57.78   13.284%   $65.4555   $65.46   $65.45   $65.50  
  Purchase #7 $163.48   4.782%   $171.2976   $171.30   $171.30   $171.30  
  7 purchase totals = $527.05       $565.4490   $565.45   $565.45   $565.50