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 $22.86   10.404%   $25.2384   $25.24   $25.25   $25.20  
  Purchase #2 $108.66   11.355%   $120.9983   $121.00   $121.00   $121.00  
  Purchase #3 $217.44   12.149%   $243.8568   $243.86   $243.85   $243.90  
  Purchase #4 $156.42   4.246%   $163.0616   $163.06   $163.05   $163.10  
  Purchase #5 $190.43   11.657%   $212.6284   $212.63   $212.65   $212.60  
  Purchase #6 $55.66   6.873%   $59.4855   $59.49   $59.50   $59.50  
  Purchase #7 $198.53   4.870%   $208.1984   $208.20   $208.20   $208.20  
  7 purchase totals = $950.00       $1,033.4674   $1,033.48   $1,033.50   $1,033.50