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 $66.84   3.488%   $69.1714   $69.17   $69.15   $69.20  
  Purchase #2 $218.97   10.325%   $241.5787   $241.58   $241.60   $241.60  
  Purchase #3 $223.45   6.120%   $237.1251   $237.13   $237.15   $237.10  
  Purchase #4 $33.59   6.314%   $35.7109   $35.71   $35.70   $35.70  
  Purchase #5 $114.90   11.491%   $128.1032   $128.10   $128.10   $128.10  
  Purchase #6 $137.94   3.479%   $142.7389   $142.74   $142.75   $142.70  
  Purchase #7 $108.47   4.229%   $113.0572   $113.06   $113.05   $113.10  
  7 purchase totals = $904.16       $967.4854   $967.49   $967.50   $967.50