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 $86.95   13.572%   $98.7509   $98.75   $98.75   $98.80  
  Purchase #2 $193.57   13.784%   $220.2517   $220.25   $220.25   $220.30  
  Purchase #3 $213.41   11.278%   $237.4784   $237.48   $237.50   $237.50  
  Purchase #4 $184.46   12.375%   $207.2869   $207.29   $207.30   $207.30  
  Purchase #5 $243.92   7.708%   $262.7214   $262.72   $262.70   $262.70  
  Purchase #6 $118.37   7.304%   $127.0157   $127.02   $127.00   $127.00  
  Purchase #7 $46.64   9.321%   $50.9873   $50.99   $51.00   $51.00  
  7 purchase totals = $1,087.32       $1,204.4923   $1,204.50   $1,204.50   $1,204.60