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 $87.73   8.667%   $95.3336   $95.33   $95.35   $95.30  
  Purchase #2 $107.68   8.802%   $117.158   $117.16   $117.15   $117.20  
  Purchase #3 $82.58   3.649%   $85.5933   $85.59   $85.60   $85.60  
  Purchase #4 $214.32   9.240%   $234.1232   $234.12   $234.10   $234.10  
  Purchase #5 $244.80   10.806%   $271.2531   $271.25   $271.25   $271.30  
  Purchase #6 $186.90   5.255%   $196.7216   $196.72   $196.70   $196.70  
  Purchase #7 $190.98   8.817%   $207.8187   $207.82   $207.80   $207.80  
  7 purchase totals = $1,114.99       $1,208.0015   $1,207.99   $1,207.95   $1,208.00