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 $72.31   5.739%   $76.4599   $76.46   $76.45   $76.50  
  Purchase #2 $75.71   13.283%   $85.7666   $85.77   $85.75   $85.80  
  Purchase #3 $6.90   3.429%   $7.1366   $7.14   $7.15   $7.10  
  Purchase #4 $157.38   5.509%   $166.0501   $166.05   $166.05   $166.10  
  Purchase #5 $89.70   8.809%   $97.6017   $97.60   $97.60   $97.60  
  Purchase #6 $196.51   5.215%   $206.758   $206.76   $206.75   $206.80  
  Purchase #7 $85.37   8.544%   $92.664   $92.66   $92.65   $92.70  
  7 purchase totals = $683.88       $732.4369   $732.44   $732.40   $732.60