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 $184.34   11.414%   $205.3806   $205.38   $205.40   $205.40  
  Purchase #2 $166.49   11.568%   $185.7496   $185.75   $185.75   $185.70  
  Purchase #3 $162.94   3.166%   $168.0987   $168.10   $168.10   $168.10  
  Purchase #4 $35.69   10.692%   $39.506   $39.51   $39.50   $39.50  
  Purchase #5 $52.46   6.652%   $55.9496   $55.95   $55.95   $55.90  
  Purchase #6 $239.64   5.162%   $252.0102   $252.01   $252.00   $252.00  
  Purchase #7 $94.95   13.360%   $107.6353   $107.64   $107.65   $107.60  
  7 purchase totals = $936.51       $1,014.3300   $1,014.34   $1,014.35   $1,014.20