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 $72.29   5.203%   $76.0512   $76.05   $76.05   $76.10  
  Purchase #2 $214.95   9.388%   $235.1295   $235.13   $235.15   $235.10  
  Purchase #3 $144.85   6.513%   $154.2841   $154.28   $154.30   $154.30  
  Purchase #4 $183.60   3.809%   $190.5933   $190.59   $190.60   $190.60  
  Purchase #5 $238.85   9.452%   $261.4261   $261.43   $261.45   $261.40  
  Purchase #6 $191.75   12.187%   $215.1186   $215.12   $215.10   $215.10  
  Purchase #7 $85.52   12.637%   $96.3272   $96.33   $96.35   $96.30  
  7 purchase totals = $1,131.81       $1,228.9300   $1,228.93   $1,229.00   $1,228.90