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 $76.60   13.361%   $86.8345   $86.83   $86.85   $86.80  
  Purchase #2 $177.49   10.825%   $196.7033   $196.70   $196.70   $196.70  
  Purchase #3 $32.29   4.294%   $33.6765   $33.68   $33.70   $33.70  
  Purchase #4 $245.76   8.724%   $267.2001   $267.20   $267.20   $267.20  
  Purchase #5 $121.88   5.103%   $128.0995   $128.10   $128.10   $128.10  
  Purchase #6 $40.49   6.110%   $42.9639   $42.96   $42.95   $43.00  
  Purchase #7 $221.58   5.307%   $233.3393   $233.34   $233.35   $233.30  
  7 purchase totals = $916.09       $988.8171   $988.81   $988.85   $988.80