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 $197.85   5.554%   $208.8386   $208.84   $208.85   $208.80  
  Purchase #2 $50.31   10.701%   $55.6937   $55.69   $55.70   $55.70  
  Purchase #3 $235.97   5.377%   $248.6581   $248.66   $248.65   $248.70  
  Purchase #4 $173.56   11.707%   $193.8787   $193.88   $193.90   $193.90  
  Purchase #5 $75.41   4.680%   $78.9392   $78.94   $78.95   $78.90  
  Purchase #6 $206.86   13.658%   $235.1129   $235.11   $235.10   $235.10  
  Purchase #7 $127.60   13.873%   $145.3019   $145.30   $145.30   $145.30  
  7 purchase totals = $1,067.56       $1,166.4231   $1,166.42   $1,166.45   $1,166.40