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 $31.99   10.753%   $35.4299   $35.43   $35.45   $35.40  
  Purchase #2 $134.42   9.775%   $147.5596   $147.56   $147.55   $147.60  
  Purchase #3 $186.71   5.117%   $196.264   $196.26   $196.25   $196.30  
  Purchase #4 $65.68   11.704%   $73.3672   $73.37   $73.35   $73.40  
  Purchase #5 $181.29   5.314%   $190.9238   $190.92   $190.90   $190.90  
  Purchase #6 $201.77   9.757%   $221.4567   $221.46   $221.45   $221.50  
  Purchase #7 $193.43   4.872%   $202.8539   $202.85   $202.85   $202.90  
  7 purchase totals = $995.29       $1,067.8551   $1,067.85   $1,067.80   $1,068.00