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 $46.66   4.447%   $48.735   $48.74   $48.75   $48.70  
  Purchase #2 $49.57   4.529%   $51.815   $51.82   $51.80   $51.80  
  Purchase #3 $39.93   7.453%   $42.906   $42.91   $42.90   $42.90  
  Purchase #4 $214.96   9.417%   $235.2028   $235.20   $235.20   $235.20  
  Purchase #5 $20.37   5.705%   $21.5321   $21.53   $21.55   $21.50  
  Purchase #6 $213.65   7.377%   $229.411   $229.41   $229.40   $229.40  
  Purchase #7 $76.48   13.274%   $86.632   $86.63   $86.65   $86.60  
  7 purchase totals = $661.62       $716.2339   $716.24   $716.25   $716.10