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 $143.92   6.724%   $153.5972   $153.60   $153.60   $153.60  
  Purchase #2 $212.32   8.197%   $229.7239   $229.72   $229.70   $229.70  
  Purchase #3 $111.84   11.351%   $124.535   $124.54   $124.55   $124.50  
  Purchase #4 $210.43   12.457%   $236.6433   $236.64   $236.65   $236.60  
  Purchase #5 $176.29   6.321%   $187.4333   $187.43   $187.45   $187.40  
  Purchase #6 $171.38   6.656%   $182.7871   $182.79   $182.80   $182.80  
  Purchase #7 $137.47   6.434%   $146.3148   $146.31   $146.30   $146.30  
  7 purchase totals = $1,163.65       $1,261.0346   $1,261.03   $1,261.05   $1,260.90