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 $64.61   6.239%   $68.641   $68.64   $68.65   $68.60  
  Purchase #2 $233.88   5.810%   $247.4684   $247.47   $247.45   $247.50  
  Purchase #3 $119.30   6.127%   $126.6095   $126.61   $126.60   $126.60  
  Purchase #4 $156.74   7.626%   $168.693   $168.69   $168.70   $168.70  
  Purchase #5 $163.76   7.216%   $175.5769   $175.58   $175.60   $175.60  
  Purchase #6 $192.63   10.754%   $213.3454   $213.35   $213.35   $213.30  
  Purchase #7 $231.25   5.665%   $244.3503   $244.35   $244.35   $244.40  
  7 purchase totals = $1,162.17       $1,244.6845   $1,244.69   $1,244.70   $1,244.70