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 $59.61   5.226%   $62.7252   $62.73   $62.75   $62.70  
  Purchase #2 $163.48   8.625%   $177.5802   $177.58   $177.60   $177.60  
  Purchase #3 $43.40   10.378%   $47.9041   $47.90   $47.90   $47.90  
  Purchase #4 $154.87   3.214%   $159.8475   $159.85   $159.85   $159.80  
  Purchase #5 $227.47   11.431%   $253.4721   $253.47   $253.45   $253.50  
  Purchase #6 $73.60   7.643%   $79.2252   $79.23   $79.25   $79.20  
  Purchase #7 $174.65   6.162%   $185.4119   $185.41   $185.40   $185.40  
  7 purchase totals = $897.08       $966.1662   $966.17   $966.20   $966.10