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 $214.94   8.846%   $233.9536   $233.95   $233.95   $234.00  
  Purchase #2 $231.86   3.299%   $239.5091   $239.51   $239.50   $239.50  
  Purchase #3 $70.72   13.503%   $80.2693   $80.27   $80.25   $80.30  
  Purchase #4 $91.71   3.773%   $95.1702   $95.17   $95.15   $95.20  
  Purchase #5 $150.99   9.155%   $164.8131   $164.81   $164.80   $164.80  
  Purchase #6 $228.83   8.408%   $248.07   $248.07   $248.05   $248.10  
  Purchase #7 $84.81   8.206%   $91.7695   $91.77   $91.75   $91.80  
  7 purchase totals = $1,073.86       $1,153.5548   $1,153.55   $1,153.45   $1,153.70