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 $176.82   9.500%   $193.6179   $193.62   $193.60   $193.60  
  Purchase #2 $129.48   3.713%   $134.2876   $134.29   $134.30   $134.30  
  Purchase #3 $196.43   8.265%   $212.6649   $212.66   $212.65   $212.70  
  Purchase #4 $242.39   4.602%   $253.5448   $253.54   $253.55   $253.50  
  Purchase #5 $124.51   5.264%   $131.0642   $131.06   $131.05   $131.10  
  Purchase #6 $176.57   12.371%   $198.4135   $198.41   $198.40   $198.40  
  Purchase #7 $218.59   3.533%   $226.3128   $226.31   $226.30   $226.30  
  7 purchase totals = $1,264.79       $1,349.9057   $1,349.89   $1,349.85   $1,349.90