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 $208.98   11.755%   $233.5456   $233.55   $233.55   $233.50  
  Purchase #2 $216.60   9.284%   $236.7091   $236.71   $236.70   $236.70  
  Purchase #3 $29.45   4.363%   $30.7349   $30.73   $30.75   $30.70  
  Purchase #4 $250.68   6.142%   $266.0768   $266.08   $266.10   $266.10  
  Purchase #5 $203.68   8.405%   $220.7993   $220.80   $220.80   $220.80  
  Purchase #6 $151.42   4.411%   $158.0991   $158.10   $158.10   $158.10  
  Purchase #7 $74.66   3.207%   $77.0543   $77.05   $77.05   $77.10  
  7 purchase totals = $1,135.47       $1,223.0191   $1,223.02   $1,223.05   $1,223.00