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 $84.37   13.837%   $96.0443   $96.04   $96.05   $96.00  
  Purchase #2 $193.58   11.194%   $215.2493   $215.25   $215.25   $215.20  
  Purchase #3 $108.33   5.626%   $114.4246   $114.42   $114.40   $114.40  
  Purchase #4 $221.97   13.633%   $252.2312   $252.23   $252.25   $252.20  
  Purchase #5 $57.99   5.514%   $61.1876   $61.19   $61.20   $61.20  
  Purchase #6 $193.55   10.279%   $213.445   $213.45   $213.45   $213.40  
  Purchase #7 $167.67   13.832%   $190.8621   $190.86   $190.85   $190.90  
  7 purchase totals = $1,027.46       $1,143.4441   $1,143.44   $1,143.45   $1,143.30