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 $248.33   5.745%   $262.5966   $262.60   $262.60   $262.60  
  Purchase #2 $232.55   13.271%   $263.4117   $263.41   $263.40   $263.40  
  Purchase #3 $215.88   12.731%   $243.3637   $243.36   $243.35   $243.40  
  Purchase #4 $80.50   4.461%   $84.0911   $84.09   $84.10   $84.10  
  Purchase #5 $222.59   5.492%   $234.8146   $234.81   $234.80   $234.80  
  Purchase #6 $159.55   9.639%   $174.929   $174.93   $174.95   $174.90  
  Purchase #7 $210.43   5.609%   $222.233   $222.23   $222.25   $222.20  
  7 purchase totals = $1,369.83       $1,485.4397   $1,485.43   $1,485.45   $1,485.40