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 $68.46   11.398%   $76.2631   $76.26   $76.25   $76.30  
  Purchase #2 $116.94   13.584%   $132.8251   $132.83   $132.85   $132.80  
  Purchase #3 $22.61   4.710%   $23.6749   $23.67   $23.65   $23.70  
  Purchase #4 $123.39   3.687%   $127.9394   $127.94   $127.95   $127.90  
  Purchase #5 $30.78   5.714%   $32.5388   $32.54   $32.55   $32.50  
  Purchase #6 $104.66   5.339%   $110.2478   $110.25   $110.25   $110.20  
  Purchase #7 $106.79   12.523%   $120.1633   $120.16   $120.15   $120.20  
  7 purchase totals = $573.63       $623.6524   $623.65   $623.65   $623.60