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 $193.28   11.355%   $215.2269   $215.23   $215.25   $215.20  
  Purchase #2 $182.90   5.370%   $192.7217   $192.72   $192.70   $192.70  
  Purchase #3 $43.30   6.500%   $46.1145   $46.11   $46.10   $46.10  
  Purchase #4 $186.86   10.815%   $207.0689   $207.07   $207.05   $207.10  
  Purchase #5 $12.54   12.157%   $14.0645   $14.06   $14.05   $14.10  
  Purchase #6 $186.50   11.239%   $207.4607   $207.46   $207.45   $207.50  
  Purchase #7 $124.31   6.106%   $131.9004   $131.90   $131.90   $131.90  
  7 purchase totals = $929.69       $1,014.5576   $1,014.55   $1,014.50   $1,014.60