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 $217.28   8.729%   $236.2464   $236.25   $236.25   $236.20  
  Purchase #2 $92.71   13.195%   $104.9431   $104.94   $104.95   $104.90  
  Purchase #3 $83.53   5.342%   $87.9922   $87.99   $88.00   $88.00  
  Purchase #4 $207.41   6.291%   $220.4582   $220.46   $220.45   $220.50  
  Purchase #5 $82.66   11.680%   $92.3147   $92.31   $92.30   $92.30  
  Purchase #6 $173.55   10.625%   $191.9897   $191.99   $192.00   $192.00  
  Purchase #7 $76.89   4.488%   $80.3408   $80.34   $80.35   $80.30  
  7 purchase totals = $934.03       $1,014.2851   $1,014.28   $1,014.30   $1,014.20