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 $187.54   13.869%   $213.5499   $213.55   $213.55   $213.50  
  Purchase #2 $164.26   9.200%   $179.3719   $179.37   $179.35   $179.40  
  Purchase #3 $219.95   6.640%   $234.5547   $234.55   $234.55   $234.60  
  Purchase #4 $17.78   7.257%   $19.0703   $19.07   $19.05   $19.10  
  Purchase #5 $167.62   4.664%   $175.4378   $175.44   $175.45   $175.40  
  Purchase #6 $118.45   5.321%   $124.7527   $124.75   $124.75   $124.80  
  Purchase #7 $240.93   3.312%   $248.9096   $248.91   $248.90   $248.90  
  7 purchase totals = $1,116.53       $1,195.6469   $1,195.64   $1,195.60   $1,195.70