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 $33.36   7.446%   $35.844   $35.84   $35.85   $35.80  
  Purchase #2 $108.34   10.670%   $119.8999   $119.90   $119.90   $119.90  
  Purchase #3 $176.89   6.166%   $187.797   $187.80   $187.80   $187.80  
  Purchase #4 $56.33   13.606%   $63.9943   $63.99   $64.00   $64.00  
  Purchase #5 $131.63   5.841%   $139.3185   $139.32   $139.30   $139.30  
  Purchase #6 $239.69   4.788%   $251.1664   $251.17   $251.15   $251.20  
  Purchase #7 $139.61   3.340%   $144.273   $144.27   $144.25   $144.30  
  7 purchase totals = $885.85       $942.2931   $942.29   $942.25   $942.30