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 $39.58   11.416%   $44.0985   $44.10   $44.10   $44.10  
  Purchase #2 $159.87   6.150%   $169.702   $169.70   $169.70   $169.70  
  Purchase #3 $46.73   9.769%   $51.2951   $51.30   $51.30   $51.30  
  Purchase #4 $248.36   4.499%   $259.5337   $259.53   $259.55   $259.50  
  Purchase #5 $63.76   8.413%   $69.1241   $69.12   $69.10   $69.10  
  Purchase #6 $86.37   9.705%   $94.7522   $94.75   $94.75   $94.80  
  Purchase #7 $66.27   5.765%   $70.0905   $70.09   $70.10   $70.10  
  7 purchase totals = $710.94       $758.5961   $758.59   $758.60   $758.60