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 $70.56   3.471%   $73.0091   $73.01   $73.00   $73.00  
  Purchase #2 $190.74   3.433%   $197.2881   $197.29   $197.30   $197.30  
  Purchase #3 $74.84   5.420%   $78.8963   $78.90   $78.90   $78.90  
  Purchase #4 $228.87   9.379%   $250.3357   $250.34   $250.35   $250.30  
  Purchase #5 $193.96   7.536%   $208.5768   $208.58   $208.60   $208.60  
  Purchase #6 $234.35   13.830%   $266.7606   $266.76   $266.75   $266.80  
  Purchase #7 $172.33   8.728%   $187.371   $187.37   $187.35   $187.40  
  7 purchase totals = $1,165.65       $1,262.2376   $1,262.25   $1,262.25   $1,262.30