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 $54.40   11.458%   $60.6332   $60.63   $60.65   $60.60  
  Purchase #2 $174.50   12.412%   $196.1589   $196.16   $196.15   $196.20  
  Purchase #3 $40.48   12.611%   $45.5849   $45.58   $45.60   $45.60  
  Purchase #4 $164.75   7.149%   $176.528   $176.53   $176.55   $176.50  
  Purchase #5 $220.28   5.415%   $232.2082   $232.21   $232.20   $232.20  
  Purchase #6 $171.25   8.772%   $186.2721   $186.27   $186.25   $186.30  
  Purchase #7 $245.40   8.812%   $267.0246   $267.02   $267.00   $267.00  
  7 purchase totals = $1,071.06       $1,164.4099   $1,164.40   $1,164.40   $1,164.40