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 $72.70   5.848%   $76.9515   $76.95   $76.95   $77.00  
  Purchase #2 $205.60   4.662%   $215.1851   $215.19   $215.20   $215.20  
  Purchase #3 $146.65   7.452%   $157.5784   $157.58   $157.60   $157.60  
  Purchase #4 $112.76   3.553%   $116.7664   $116.77   $116.75   $116.80  
  Purchase #5 $156.91   11.715%   $175.292   $175.29   $175.30   $175.30  
  Purchase #6 $98.73   11.524%   $110.1076   $110.11   $110.10   $110.10  
  Purchase #7 $247.44   5.659%   $261.4426   $261.44   $261.45   $261.40  
  7 purchase totals = $1,040.79       $1,113.3236   $1,113.33   $1,113.35   $1,113.40