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 $43.90   8.544%   $47.6508   $47.65   $47.65   $47.70  
  Purchase #2 $183.58   13.426%   $208.2275   $208.23   $208.25   $208.20  
  Purchase #3 $67.86   8.589%   $73.6885   $73.69   $73.70   $73.70  
  Purchase #4 $20.29   5.547%   $21.4155   $21.42   $21.40   $21.40  
  Purchase #5 $167.71   4.199%   $174.7521   $174.75   $174.75   $174.80  
  Purchase #6 $157.66   13.770%   $179.3698   $179.37   $179.35   $179.40  
  Purchase #7 $148.75   9.496%   $162.8753   $162.88   $162.90   $162.90  
  7 purchase totals = $789.75       $867.9795   $867.99   $868.00   $868.10