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 $13.90   3.282%   $14.3562   $14.36   $14.35   $14.40  
  Purchase #2 $208.61   13.874%   $237.5526   $237.55   $237.55   $237.60  
  Purchase #3 $249.33   8.811%   $271.2985   $271.30   $271.30   $271.30  
  Purchase #4 $208.92   6.719%   $222.9573   $222.96   $222.95   $223.00  
  Purchase #5 $169.93   12.743%   $191.5842   $191.58   $191.60   $191.60  
  Purchase #6 $146.35   6.748%   $156.2257   $156.23   $156.25   $156.20  
  Purchase #7 $64.26   4.251%   $66.9917   $66.99   $67.00   $67.00  
  7 purchase totals = $1,061.30       $1,160.9662   $1,160.97   $1,161.00   $1,161.10