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 $233.67   4.858%   $245.0217   $245.02   $245.00   $245.00  
  Purchase #2 $175.60   6.300%   $186.6628   $186.66   $186.65   $186.70  
  Purchase #3 $61.55   9.656%   $67.4933   $67.49   $67.50   $67.50  
  Purchase #4 $182.55   8.222%   $197.5593   $197.56   $197.55   $197.60  
  Purchase #5 $238.27   11.237%   $265.0444   $265.04   $265.05   $265.00  
  Purchase #6 $153.61   6.379%   $163.4088   $163.41   $163.40   $163.40  
  Purchase #7 $85.33   6.814%   $91.1444   $91.14   $91.15   $91.10  
  7 purchase totals = $1,130.58       $1,216.3347   $1,216.32   $1,216.30   $1,216.30