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 $96.99   9.494%   $106.1982   $106.20   $106.20   $106.20  
  Purchase #2 $127.39   5.381%   $134.2449   $134.24   $134.25   $134.20  
  Purchase #3 $143.69   9.441%   $157.2558   $157.26   $157.25   $157.30  
  Purchase #4 $119.60   10.245%   $131.853   $131.85   $131.85   $131.90  
  Purchase #5 $196.26   11.854%   $219.5247   $219.52   $219.50   $219.50  
  Purchase #6 $239.34   11.339%   $266.4788   $266.48   $266.50   $266.50  
  Purchase #7 $172.91   11.606%   $192.9779   $192.98   $193.00   $193.00  
  7 purchase totals = $1,096.18       $1,208.5333   $1,208.53   $1,208.55   $1,208.60