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 $94.58   4.124%   $98.4805   $98.48   $98.50   $98.50  
  Purchase #2 $196.50   6.272%   $208.8245   $208.82   $208.80   $208.80  
  Purchase #3 $155.92   12.377%   $175.2182   $175.22   $175.20   $175.20  
  Purchase #4 $231.60   5.706%   $244.8151   $244.82   $244.80   $244.80  
  Purchase #5 $35.70   3.481%   $36.9427   $36.94   $36.95   $36.90  
  Purchase #6 $118.43   13.660%   $134.6075   $134.61   $134.60   $134.60  
  Purchase #7 $145.48   11.756%   $162.5826   $162.58   $162.60   $162.60  
  7 purchase totals = $978.21       $1,061.4711   $1,061.47   $1,061.45   $1,061.40